Note: Descriptions are shown in the official language in which they were submitted.
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METHODS AND SYSTEMS FOR ASSESSING COGNITIVE FUNCTION
FIELD OF THE INVENTION
[0001] The present invention pertains to the field of neuropsychological
testing and in
particular to the tracking of eye movement to assess cognitive function.
BACKGROUND
[0002] The current standard in cognitive assessments includes a number of
paper-and-pencil
tasks, tasks that require motor movement, and tasks that require verbal
interaction with the
clinician/researcher who is conducting the assessment. If a client has motor
infirmities, or cannot
respond verbally (e.g., due to stroke), assessment may not be possible or the
results of such
testing may be inaccurate or incomplete. The current standards of
neuropsychological testing are
also time-consuming.
[0003] Examples of commonly used cognitive assessments are paper-based tests
such as the
Mini Mental Status Exam (MMSE) distributed by PAR, the Montreal Cognitive
Assessment
(MOCA), the Wechsler Memory Scale (WMS) distributed by Pearson, the Wechsler
Adult
Intelligence Scale - iv (WAIS-IV). Delis-Kaplan Executive Function System (D-
KEFS),
Judgment of Line Orientation, Benton Face Recognition, and Line Cancellation
Tests.
[0004] Recent research has suggested that eye movement markers may be a more
sensitive and
precise index of cognitive functioning than standard paper-and-pencil
neuropsychological
assessments. Eyetracking-based neuropsychological assessment would therefore
obviate the
need for verbal and motor (e.g., hand) responses.
[0005] Therefore there is a need for methods and systems which apply this
known correlation
between cognitive function and eye movement to assess cognitive function
and/or cognitive
impairment in test subjects.
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[0006] There is also a need for mobile monitoring systems for assessing
cognitive function
and/or cognitive impairment which are inexpensive and suitable for use in
clinical and
community settings, and which can provide an accurate assessment in a short
period of time.
[0007] This background information is provided to reveal information believed
by the
applicant to be of possible relevance to the present invention. No admission
is necessarily
intended, nor should be construed, that any of the preceding information
constitutes prior art
against the present invention.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to provide methods and systems
for assessing
cognitive function. In accordance with an aspect of the present invention,
there is provided a
method of assessing cognitive function in a subject, comprising the steps of
(a) presenting a
plurality of images to the subject, wherein the plurality of images comprises
a first subset of
images and a second subset of images; (b) monitoring eye movements of the
subject during
presentation of the first subset of images to obtain first eye movement data;
(c) monitoring eye
movements of the subject during presentation of the second subset of images to
obtain second
eye movement data; (d) comparing the first eye movement data and the second
eye movement
data to determine an index of cognitive function; and (e) correlating the
index of cognitive
function with a degree of cognitive function in the subject, thereby assessing
the cognitive
function. In accordance with this aspect, the monitoring steps are carried out
using an optical
eyetracking system.
[0009] In accordance with another aspect of the present invention, there is
provided a system
for assessing cognitive function in a subject, comprising: a presentation
module configured to
present a first subset of images and a second subset of images to the subject;
an optical
eyetracking module configured to monitor the eye movement of the subject
during presentation
of the first subset of images and second subset of images to generate first
eye movement data and
second eye movement data, respectively; and a computing module communicatively
linked to the
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optical eyetracking module and optionally the presentation module, wherein the
computing
module is configured to receive the first eye movement data and the second eye
movement data,
compare the first eye movement data and the second eye movement data to
determine an index of
cognitive function, and correlate the index of cognitive function with a
degree of cognitive
function in the subject, thereby assessing the cognitive function.
DETAILED DESCRIPTION OF THE INVENTION
[00101 Unless defined otherwise, all technical and scientific terms used
herein have the same
meaning as commonly understood by one of ordinary skill in the art to which
this invention
belongs.
The present invention correlates a subject's eye movement when viewing an
image with the
subject's cognitive function. Examples of cognitive functions that can be
assessed using the
methods and systems of the present invention include, but are not limited to,
long-term memory,
short-term memory, working memory, language processing and comprehension,
symbol
processing, attention, perception, processing speed, reasoning, emotion
processing, emotion
recognition, executive function, and inhibition.
[0011) The present invention therefore employs eye movement markers to provide
an index
of cognition in an efficient manner and without requiring explicit verbal
responses from the
client. Eyetracking-based neuropsychological assessments are faster for the
clinician/researcher
to administer, allow for a wider range of clients to be tested, and provide a
more precise
delineation of cognitive and underlying neural integrity.
[0012) The present invention therefore provides a method for assessing
cognitive function in a
subject, wherein a plurality of discrete images is presented to the subject,
and the subject's
response (i.e., eye movements) when viewing each image is monitored using
commercially
available eyetracking technology. Eye movement data obtained during viewing of
the images are
obtained and compared, thereby providing an index of cognition. This index of
cognition is
correlated with an assessment in cognitive function in the subject.
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[0013] In accordance with one embodiment of the present invention, the
assessment of
cognitive function includes an assessment, or diagnosis, of an impairment of
cognitive function.
In accordance with another embodiment of the present invention, the assessment
of cognitive
function includes an assessment, or diagnosis, of high cognitive function.
[0014] In one embodiment, the cognitive function being assessed using the
method of the
present invention is memory impairment. For example, for a subject with no
memory
impairment, the amount of viewing (e.g., the number of fixations, or the
amount of time the eyes
"stop" on the image) will be lower for known images or will decrease with
repeated viewing of
the same image. For a subject with memory impairment, it is expected that
there will be little
change in eye movement over the course of repeated viewing of the same image
or little
differentiation in eye movement between known and novel images.
[0015] Eye movements are used to reveal memory for familiar/known images, in
that familiar
items are typically viewed with, for example, fewer fixations or fewer
distinct regions being
sampled on the images than novel items, for individuals with intact memory.
This correlation
between eye movement and cognitive function is exploited in the present
invention, and provides
the basis for the presently disclosed methods and systems for assessing
cognitive function.
[0016] In certain embodiments of the present invention, the methods rely on
naturalistic (non-
directed) viewing. In such embodiments, the invention is suitable for
assessing subjects who are
not capable of following instructions or communicating (for example, due to
language barriers),
or responding (verbally or non-verbally) to questions or instructions.
Although the present
invention does not require verbal or response judgment from the subject during
evaluation, it is
still within the scope of the present invention to incorporate a verbal or
response judgment
component to the cognitive function assessments.
Methods of Assessing Cognitive Function
[0017] The methods of the present invention rely on the collection of data
relating to the
subject's eye movement when viewing an image. Eye movement data can be
compiled and
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analyzed in several different ways. A selection of commonly used
characterizations of viewing
are defined as follows. This list is representative, and is not intended to be
limiting.
= Number of fixations: the number of discrete pauses of the eyes for a
display.
= Fixation duration: the length of time in which the eye pauses on a display,
wherein
median or mean fixation duration to a display are calculated.
= Number of regions fixated: the number of discrete regions sampled within a
display.
= Location of fixations: the location in the image on which the eye is
fixated.
= Spatial distribution of fixations: the total area explored by the eyes on
the image.
= Temporal order of fixations
= Measurement of saccades, including parameters such as amplitude,
acceleration, velocity
and duration.
= Constraint/entropy with the spatial and temporal distributions of fixations:
how the
location or duration of the current fixation may predict the location or the
duration of the
next fixation.
= Comparison of the similarity of eye movement patterns across images, in
spatial and/or
temporal distribution.
= Characteristics of eye fixations (e.g., duration, location, number, order)
with respect to
particular regions of interest in an image.
= The number of transitions that are made by the eyes between pre-specified
regions of
interest.
= Smooth pursuit movements.
[0018] The present invention also provides for the monitoring of pupil
dilation as a measure of
cognitive function as appropriate.
[0019] Sampling of visual materials can be characterized in terms of overall
viewing at the
level of an entire experimental display, or directed viewing at the level of
regions, objects, or
stimuli within that display.
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[0020] During the course of an assessment task, a series of images is
presented to the subject.
In accordance with the present invention, each image is presented for a
predetermined period of
time, the duration of which is determined according to the assessment task
being conducted and
the type of eye movement data being sought. For example, an image may be
presented for a
shorter duration, such as, but not limited to, 100 milliseconds; an image may
also be shown for a
longer duration, such as, but not limited to, 5 seconds.
[0021] In accordance with the present invention, a plurality of images is
presented to the subject
during the course of an assessment task, wherein the plurality of images
comprises a first subset
of images and a second subset of images.
[0022] In one embodiment, the first subset of images is a single image not
previously viewed by
the subject, and the second subset of images is a single image previously
viewed by the subject.
In one embodiment, the first and second subsets of images are presented
simultaneously. In
another embodiment, the first and second subsets of images are presented
sequentially.
[0023] In one embodiment, the first subset of images consists of images not
previously viewed
by the subject, and the second subset of images consists of images previously
viewed by the
subject.
[0024] In one embodiment, the first subset of images comprises first image,
wherein the first
image has not been previously viewed by the subject, and the second subset of
images comprises
a repeated presentation of the first image. In this embodiment, eye movement
data is obtained by
monitoring the eye movements of the subject during the presentation of the
first image as well as
during each of the subsequent presentations of the first image.
[0025] In one embodiment, the first subset of images and second subset of
images each consist
of images depicting a plurality of items in a defined spatial arrangement,
wherein the first and
second subsets differ only in the relative spatial arrangement of the
plurality of items.
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[0026] In some embodiments of the present invention, a fixation screen is
presented for a
defined period of time between each test image. The duration of fixation
screen can be adjusted
to test the range of conditions under which intact versus impaired cognitive
function is observed.
[0027] The number of repetitions in a given test is that which is sufficient
to provide an index of
cognitive function. Determination of the number of repetitions is made with
consideration of
factors including, but not limited to, the length of duration of an individual
exposure, the overall
number of images presented in a given test, and/or how distinct each image is
from other images
presented in the test. Accordingly, the recitation of a number of repetitions
in the description of
any tasks disclosed herein is not intended to be limiting, and it is
understood that any number of
repetitions as is determined by a worker skilled in the relevant art to be
sufficient to provide an
index of cognitive function falls within the scope of the present invention.
[0028] The duration of each task is variable, and depends on, for example, the
number of
images presented, the duration of the familiarization phase for each image,
and the amount of
repetition for each image. Where a fixation screen is used between
presentation of each image in
the familiarization and test phases, the duration of the fixation screen will
also impact the overall
duration of the task. Where a delay between the familiarization phase of each
image and the
subsequent test display of either the same or altered image, is employed, the
overall duration of
the task is impacted.
Tasks for Assessment of Cognitive Function
[0029] The methods of the present invention can be carried out using a variety
of different tasks
to assess cognitive function. Non-limiting examples of such tasks are set out
below.
Single Object Memory Task (Known/Familiar vs. Unknown/Novel)
[0030] The task is designed to examine visual memory for single objects, which
is thought to
rely on visual cortical areas.
[0031] In this task, the subject is presented with a series of images of
distinct items (e.g., faces,
objects, abstract non-nameable images), wherein each image is presented for a
predetermined
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length of time. The series of images includes a combination of novel (unknown
or not previously
viewed) and known (familiar or previously viewed) images. Novel images are
presented only
one time during the course of the task. Presentation of the items will be
randomized. Known
images can include images familiar to the subject or are otherwise known from
the subject's
previous experience. The known images can also include images that are
presented repeatedly
over the course of the test. This repeated presentation of an image is
referred to as a
familiarization phase.
[0032] The length of time for viewing the images during this familiarization
phase can be
adjusted to test the range under which subsequent eye movement memory effects
(as described
below) are observed. A subset of the presented items are shown once only
(novel), other items
are each shown multiple times (repeated). In one embodiment, there is a
fixation screen in
between presentation of each item.
[0033] The subject's eye movements are monitored during the viewing of each
image. It is
expected that, for a subject with no memory impairment, the amount of viewing
(for example,
but not limited to, the number of fixations, or the amount of time the eyes
"stop" on the image)
will decrease across repetitions. Also, the spatial distribution of the eye
movements across the
image should decrease (i.e., the total area explored by the eyes on the
image).
[0034] This task can be adapted to test higher memory function/achievement, by
making the
memory test more difficult by including a subset of novel and repeated images
that are very
similar to each other, thereby making it more difficult to form separate
memories of each and
distinguish novel from repeated.
[0035] A ratio of novel:repeated is generated for each eye movement measure
(e.g., number
and/or duration of fixations) for each level of repetition. A score of 1 (or
below) indicates that
there is no memory that has been maintained for the repeated objects (i.e.,
viewing of novel items
is equal to viewing of repeated items). A score higher than 1 indicates that
the subject has
memory for those items that are repeated.
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[0036] Examining the ratios across repetition levels (e.g., 1 exposure, 3
exposures), or
familiarization duration (e.g., 1 second each viewing, 5 seconds each
viewing), indicates how
fast memories are being formed. Additionally, a slope of the ratios across
levels captures the rate
of learning (a slope of 0 indicates no learning, a positive slope indicates
learning).
Visual Paired Comparison Task
[0037] This task is designed to examine visual memory for single objects
across varying delays,
which is thought to rely on visual cortical areas, and the medial temporal
lobe, particularly as the
delay increases.
[0038] In the visual paired comparison task, two images are presented
simultaneously, one image
being a known (previously viewed/repeated) image, and the other being a novel
image. Again
the known image can include images familiar to the subject or are otherwise
known from the
subject's previous experience. The known images can also include images that
are presented
repeatedly during a familiarization phase.
[0039] During such a familiarization phase, the subject is shown a series of
images of distinct
items (e.g., faces, objects, abstract non-nameable images), one at a time, for
a predetermined
period of time. Items are repeated multiple times. In one embodiment, there is
a fixation screen
in between presentation of each item. The amount of repetition of each item,
the period of
viewing time and the duration of fixation screen are each independently
adjustable to test the
range under which subsequent eye movement memory effects are observed.
[0040] In one embodiment, a delay is imposed after the familiarization phase
and the beginning
of the test phase. This delay between viewing of a stimulus in the
familiarization phase and
viewing of the same stimulus in the test phase is adjustable for each item to
examine immediate
versus longer-term memory. Subjects are shown pairs of items, one item on each
side of the
screen, for a pre-determined amount of time. These pairs of items consist of
one previously
viewed (repeated) image, and one novel image. In one embodiment, there is a
fixation screen in
between each presentation of a pair of items. Presentation of the items is
pseudo-randomized to
capture a range of delay conditions, and examine memory performance over time.
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[0041] This task can be adapted to test higher memory function/achievement by
varying how
similar the novel and known images are. The more similar two images are, the
more difficult it
should be to distinguish between the two, but if a subject has superior
memory, their eye
movements will indicate that they are able to distinguish between very similar
images.
[0042] The subject's eye movements are monitored during the viewing of each
pair of images. It
is expected that a subject with no memory impairment should direct more eye
movements (e.g.,
duration of viewing, fixations) to the novel item when the pairs of items
(novel + repeated) are
presented. A ratio of novel:repeated is generated for each eye movement
measure. A score of 1
(or below) indicates that there is no memory that has been maintained for the
repeated objects
(i.e., viewing of novel items is equal to viewing of repeated items). A score
higher than 1
indicates that the subject has memory for those items that are repeated.
[0043] A slope can be generated for the ratios across the two delays to
determine the stability of
memory over time (here, a slope of 0 indicates no change in memory over time,
a negative slope
indicates forgetting over longer delays, a positive slope indicates impaired
shorter-term memory
processes relative to longer-term memory processes).
Memory for Spatial Associations
[0044] The task is designed to examine visual memory for the spatial
relationships among
objects, which is thought to rely on the prefrontal cortex (at short delays),
and medial temporal
lobe (at short and longer delays)
[0045] In this task, the subject is presented with a series of images in a
familiarization phase,
wherein each image is presented for a predetermined length of time, and the
length of time for
viewing the images during this familiarization phase can be adjusted to test
the range under
which subsequent eye movement memory effects are observed. Each of the images
comprises a
plurality of objects (including, but not limited to, known objects, abstract
non-nameable objects,
faces) in a defined spatial arrangement. Examples include images of everyday
scenes (e.g., an
arrangement of furniture in a living room), or an assembly of everyday objects
in a defined
spatial arrangement.
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[0046] Following the familiarization phase, a delay is imposed prior to the
beginning of the test
phase. Images in the test phase consist of those that are re-presented in the
same exact format
(repeated images), and images that have been seen in the familiarization
phase, but in the test
phase have been altered (altered images). This alteration can be in the form
of a change in the
spatial arrangement of the objects, or in the removal or addition of an object
from the image.
The delay between viewing of a stimulus in the familiarization phase and
viewing of the same or
altered stimulus in the test phase is adjustable for each item to examine
immediate versus longer-
term memory. In one embodiment, there is a fixation screen in between each
presentation of a
pair of items. Presentation of the items is pseudo-randomized to capture a
range of delay
conditions, and examine memory performance over time.
[0047] This task can be adapted to test higher memory function/achievement, by
making the
memory test more difficult by including a subset of altered and repeated
images that are very
similar to each other, thereby making it more difficult to form separate
memories of each and
distinguish altered from repeated.
[0048] The subject's eye movements are monitored during the viewing of each
image. It is
expected that a subject with no memory impairment should distinguish between
repeated images
and altered images. Specifically, viewing should be preferentially directed
(e.g., number and/or
duration of fixations) to the location of the image that has undergone a
change in the altered
images compared to a similar region of the repeated mages
[0049] A ratio of altered:repeated is generated for each eye movement measure
for each delay
condition. A score of 1 (or below) indicates that there is no memory that has
been maintained for
the spatial arrangements of the objects (i.e., viewing of altered scenes is
similar to viewing of
repeated scenes). A score higher than I indicates that viewers have memory for
the spatial
arrangements of the objects within the scenes.
[0050] Examining the slope of the ratios across delay conditions levels
(immediate, short, long)
indicates how fast memories are formed/forgotten (a slope of 0 indicates no
difference between
shorter-term and longer-term memory processes, a negative slope indicates
forgetting over longer
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delays, a positive slope indicates impaired shorter-term memory processes
relative to longer-term
memory processes).
Emotion Processing Task
[0051] This task is designed to examine a subject's ability to process and
distinguish emotions,
which is typically disrupted in disorders such as autism spectrum disorders,
in people who have
lesions to the amygdala, and in people who have depression.
[0052] In this task, a subject is shown a series of distinct faces expressing
different emotions
(including but not limited to, neutral, anger, disgust, fear, happiness), one
at a time. Some faces
may be presented in isolation, whereas others may be presented within a
context that is either
congruent or incongruent with the emotion that is expressed by the face (e.g.,
a face displaying
disgust is presented with a body conveying the emotion of anger) The length of
time for
viewing the images during this familiarization phase can be adjusted to test
the range under
which successful emotion processing can be observed. Presentation of the items
is randomized.
In one embodiment, there is a fixation screen in between presentation of each
item.
[0053] It is expected that, in subjects whose ability to process and
distinguish emotions is intact,
the distribution of viewing across (e.g., number and/or duration of fixations)
the face features
should distinguish between the different emotions, and such viewing should be
impacted by the
context onto which the face is presented.
[0054] Ratios that contrast across the different emotion conditions are
generated for each eye
movement measure of viewing to the face and/or face features (e.g.
anger:disgust). A score of I
(or below) indicates that there the viewer does not distinguish between the
emotions presented,
whereas a change from 1 indicates an ability to process and distinguish
between emotions.
Categorization/Symbol Processing/Language Comprehension Task
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[0055] This task is designed to examine the ability of the subject to process
spoken and/or
written language, evaluate and categorize objects. Deficits in these abilities
may be present in
disorders including, but not limited to, dementia and aphasia.
[0056] In this task, a subject is shown a series of images that depict one or
more objects and/or
people. In one embodiment, the images involve the objects and/or people
interacting or
otherwise engaging in a particular action (e.g., one person pushing another).
In another
embodiment, the objects and/or people are presented without any such
engagement. For
example, in such an embodiment, four circles of different shapes and sizes are
presented
simultaneously in different spatial locations on the screen, or four different
types of dogs and one
cat are presented simultaneously in different spatial locations on the screen.
Objects presented
within an image may be from the same basic, superordinate or subordinate
categories, or one or
more objects may be from a different basic, superordinate or subordinate
category as the other
objects. In one embodiment, a subset of the images is presented in isolation,
whereas other
images are accompanied by either a spoken (auditory presentation) or written
sentence. The
length of time provided for viewing the images depends on the condition
(presented in isolation,
presented with spoken sentence, presented with written sentence). In one
embodiment, there is a
fixation screen in between presentation of each item. Images (presented either
with or without
their corresponding auditory or visual sentences) may be repeated or may be
presented only once.
[0057] This task can be adapted to test higher cognitive functioning, by
making the spoken and
written word sentences more difficult (i.e., use a higher level of
vocabulary). Monitoring eye
movements while viewing the images during this modified task can reveal
comprehension of the
sentence. This task can also be modified to test higher cognitive functioning
by increasing the
similarity of the items within the symbol processing test.
[0058] It is expected that the distribution of viewing across the items should
be tied to the
accurate categorization of the items (e.g., more viewing to the item that does
not belong to the
same category). Viewing order and preference to the items within the image
should correspond
to the comprehension of the spoken/written language. For instance, the order
by which the
viewer fixates the items should correspond to the active/passive nature of the
sentence (e.g., "the
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boy pushed the girl" should elicit viewing first to the boy, then to the girl;
whereas "the girl was
pushed by the boy" should elicit viewing first to the girl and then to the
boy).
[0059] Ratios will contrast the distribution of viewing across objects. For
example, for trials in
which one object is presented amongst other objects from a different basic,
superordinate or
subordinate category, it is expected that viewing (e.g., number and/or
duration of fixations) will
be preferentially directed towards the oddball object compared to the average
of the other objects
if the viewer has comprehension regarding the semantic categorization of
objects (ratio greater
than 1). In the embodiment in which the images are presented with a spoken or
written sentence,
a score from 0-1 is also derived that indicates the preferential order of
viewing and the extent to
which the order of viewing matched the order of words as presented in auditory
or visual
sentence. A score of 1 indicates perfect concordance of viewing with the
sentence presentation,
and therefore intact symbol processing and language comprehension, whereas a
score of 0 means
no concordance between viewing with the sentence presentation, poor symbol
processing and
language comprehension.
Assessment of Visuo-Spatial Perception Task
[0060] This task is designed to examine visual attention/inattention to areas
of space within the
field of view.
[0061] In this task, a subject is shown images that depict one or more objects
and/or people.
Images are repeated, and flipped in left-right orientation. A fixation screen
is presented in
between each of the images.
[0062] It is expected that, across the collection of images, the distribution
of viewing should be
balanced across the left and right sides of the images, with reference to the
number of objects
contained within each side. The extent to which the viewer exhibits visual
neglect is evidenced
by more viewing to one side versus another.
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[0063] Ratios will contrast left:right distribution of viewing. A ratio at or
close to I indicates
little to no visual inattention; ratios that are skewed greater than 1, or
less than 1 indicate the
presence of visual inattention, and the side on which the neglect is
occurring.
Systems for Assessing Cognitive Function
[0064] The present invention demonstrates the effectiveness of using eye
movements to assess
cognitive function by monitoring a subject's eye movement while viewing a
series of images as
described, for example, in the tasks described above. Accordingly, the present
invention also
provides a system for assessing cognitive function in a subject, comprising a
presentation module
configured to present a first subset of images and a second subset of images
to the subject, and an
optical eyetracking module configured to monitor the eye movement of the
subject during
presentation of the first and second subsets of images to generate first and
second eye movement
data. In accordance with the present invention, the system further comprises a
computing
module communicatively linked to the optical eyetracking module, wherein the
computing
module is configured to receive the first and second eye movement data, and
compare them to
determine an index of cognitive function. This index of cognitive function is
correlated with a
degree of cognitive function in the subject, thereby assessing the cognitive
function.
[0065] Different computer platforms are suitable for use in the presently
disclosed system,
including, but not limited to, home computers, laptop computers, PDAs or any
mobile computer
platform.
[0066] Particularly preferred are computer platforms that are readily
transportable and/or
mobile, such as laptops, smartphones and computer tablets.
[0067] In one embodiment of the present system, the presentation module
comprises means for
displaying an image, including but not limited to a computer monitor or the
screen of a laptop or
handheld computing device. In one embodiment, the presentation module
comprises any means
for projecting images onto a screen or other suitable surface, or means for
transmitting images for
display on, for example, a television screen.
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[00681 In one embodiment of the present system, the eyetracking module
comprises a means
for tracking the eye movement of the subject while viewing images.
[00691 A number of different eyetracking technologies, including optical,
electrical or
magnetic based methods, are known in the art and are available and suitable
for monitoring eye
movement in accordance with the present invention. Particularly suitable for
use with the present
invention are optical eyetracking technologies, being typically non-invasive
and relatively
inexpensive. In one embodiment, the eyetracking module employs infrared (IR)-
based
technology. Moreover, there are a number of commercially available,
inexpensive, IR-based
technologies that can be readily adapted for use with mobile computing
platforms to provide
mobile systems for assessing cognitive function.
[00701 In one embodiment, the present assessment system comprises a
commercially available
infrared eyetracker system. Such systems include, but are not limited to,
those manufactured by
Mirametrix (Westmount, QC, Canada), SensoMotoric Instruments (SMI, Berlin,
Germany),
Applied Science Laboratories (Bedford, MA), and SR Research (Kanata, ON,
Canada).
[0071] In one embodiment, the present invention is implemented using IR LEDs
to illuminate
the eyes.
[00721 In one embodiment, eye movements are monitored using a native webcam
attached to a
home computer or laptop.
[00731 In one embodiment, the present invention incorporates a remote, IR
camera-based
eyetracking system.
[00741 The present assessment system comprises a computing module for
receiving eye
movement data from the eye tracking module, and comparing the data to
determine an index of
cognitive function. This index of cognitive function is correlated with a
degree of cognitive
function in the subject, thereby assessing the cognitive function. In one
embodiment, the
computing module is also communicatively linked to the presentation module.
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[0075] It will be appreciated that, although specific embodiments of the
invention have been
described herein for purposes of illustration, various modifications may be
made without
departing from the spirit and scope of the invention. In particular, it is
within the scope of the
invention to provide a computer program product or program element, or a
program storage or
memory device such as a solid or fluid transmission medium, magnetic or
optical wire, tape or
disc, or the like, for storing signals readable by a machine, for controlling
the operation of a
computer according to the method of the invention and/or to structure some or
all of its
components in accordance with the system of the invention.
[0076] Acts associated with the method described herein can be implemented as
coded
instructions in a computer program product. In other words, the computer
program product is a
computer-readable medium upon which software code is recorded to execute the
method when
the computer program product is loaded into memory and executed on the
microprocessor of the
wireless communication device.
[0077] Acts associated with the method described herein can be implemented as
coded
instructions in plural computer program products. For example, a first portion
of the method
may be performed using one computing device, and a second portion of the
method may be
performed using another computing device, server, or the like. In this case,
each computer
program product is a computer-readable medium upon which software code is
recorded to
execute appropriate portions of the method when a computer program product is
loaded into
memory and executed on the microprocessor of a computing device.
[0078] Further, each step of the method may be executed on any computing
device, such as a
personal computer, server, PDA, or the like and pursuant to one or more, or a
part of one or
more, program elements, modules or objects generated from any programming
language, such as
C++, Java, PL/1, or the like. In addition, each step, or a file or object or
the like implementing
each said step, may be executed by special purpose hardware or a circuit
module designed for
that purpose.
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CA 02754835 2011-10-07
[0079] The invention will now be described with reference to specific
examples. It will be
understood that the following examples are intended to describe embodiments of
the invention
and are not intended to limit the invention in any way.
EXAMPLES
EXAMPLE 1:
Task: Memory for Single Objects
[0080] Rationale: examine visual memory for single objects.
[0081] Procedure: Subjects are shown 10 distinct items (faces and/or objects),
one at a time, for
3 sec. each. Five of the items are shown once only (novel), the other 5 items
are each shown 5
times (repeated). Presentation of the items is randomized. There is a 1-second
fixation screen in
between presentation of each item.
[0082] Duration of Task: 2 minutes.
[0083] Scoring: A ratio of novel:repeated are generated for each eye movement
measure for
each level of repetition. A score of 1 (or below) indicates that there is no
memory that has been
maintained for the repeated objects (i.e., viewing of novel items is equal to
viewing of repeated
items). A score higher than 1 indicates that viewers have memory for those
items that are
repeated. Examining the ratios across repetition levels (1-5) indicates how
fast memories are
being formed. Additionally, a slope of the ratios across levels captures the
rate of learning (a
slope of 0 indicates no learning, a positive slope indicates learning).
EXAMPLE 2:
Task: Preferential Viewing (also called Visual Paired Comparison Task)
[0084] Rationale: examine visual memory for single objects across varying
delays.
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CA 02754835 2011-10-07
[0085] Procedure: Subjects are shown 10 distinct items (faces and/or objects),
one at a time, for
3 sec. each. All 10 items are repeated 5 times. There is a 1-second fixation
screen in between
each item. Following a delay (immediate test or 2 minutes), viewers are shown
10 pairs of items,
one item on each side of the screen, for 3 sec. each. These pairs of items
consist of one
previously viewed (repeated) image, and one novel image. There is a 1-second
fixation screen in
between each presentation of a pair of items. Presentation of the items is
pseudo-randomized so
that all of 2-minute delay items are studied first, followed by the immediate
study items, then the
test pairs for the immediate condition, and finally, the test pairs for the 2-
minute delay condition.
[0086] Duration of Task: 4 minutes.
[0087] Scoring: A ratio of novel:repeated is generated for the time that is
spent looking at each
item . A score of 1 (or below) indicates that there is no memory that has been
maintained for the
repeated objects (i.e., viewing of novel items is equal to viewing of repeated
items). A score
higher than I indicates that viewers have memory for those items that are
repeated. A slope is
generated for the ratios across the two delays to determine the stability of
memory over time
(here, a slope of 0 indicates no change in memory over time, a negative slope
indicates forgetting
over longer delays, a positive slope indicates impaired shorter-term memory
processes relative to
longer-term memory processes).
EXAMPLE 3:
Task: Memor for or Spatial Associations
[0088] Rationale: examine visual memory for the spatial relationships among
objects.
[0089] Procedure: Subjects are shown a series of everyday scenes (e.g., an
arrangement of
furniture in a living room) one at a time, for 3 sec. each. There are 18
scenes in total, and each
scene is shown twice. In the immediate delay condition, the second
presentation of the scene
immediately follows the first presentation of the scene. In the short delay
condition, the second
presentation of the scene occurs 8 seconds following the presentation of the
first scene (two
intervening scenes, an immediate trial, will occur). In the long delay
condition, the second
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CA 02754835 2011-10-07
presentation of the scene occurs 36 seconds following the first presentation
(intervening scenes
will include two immediate trials, two short trials, and the first
presentation of a scene from a
long delay trial). Three of the scenes in each delay condition are re-
presented in the same exact
format (repeated), three of the scenes in each delay condition contain a
change in the spatial
arrangement of the objects within the scene (altered). Presentation of the
scenes is pseudo-
randomized in order to accommodate the delay conditions. There is a 1-second
fixation screen in
between the presentation of each scene.
[00901 Duration of Task 2.5 minutes.
[00911 Scoring: A ratio of altered:repeated is generated for each eye movement
measure for each
delay condition. A score of I (or below) indicates that there is no memory
that has been
maintained for the spatial arrangements of the objects (i.e., viewing of
altered scenes is similar to
viewing of repeated scenes). A score higher than 1 indicates that viewers have
memory for the
spatial arrangements of the objects within the scenes. Examining the slope of
the ratios across
delay conditions levels (immediate, short, long) indicates how fast memories
are
formed/forgotten (a slope of 0 indicates no difference between shorter-term
and longer-term
memory processes, a negative slope indicates forgetting over longer delays, a
positive slope
indicates impaired shorter-term memory processes relative to longer-term
memory processes).
[00921 It is obvious that the foregoing embodiments of the invention are
examples and can be
varied in many ways. Such present or future variations are not to be regarded
as a departure from
the spirit and scope of the invention, and all such modifications as would be
obvious to one
skilled in the art are intended to be included within the scope of the
following claims.
