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Cognitive Neuropsychology
College 2 - Perception & Attention
chapter 5 - sensation and perception
chapter 6 - object recognition
College 3 - Perception & Attention
chapter 7 - attention
College 4 & 5 - Learning & Memory
chapter 9 - memory, part 1
chapter 9 - memory, part 2
College 6 & 7 - Cognitive Control
chapter 12 - cognitive control, part 1
chapter 12 - cognitive control, part 2
College 8 & 9 - Emotion
part 1 - emotions
part 2 - emotions
College 10 & 11 - Social Cognition
part 1 - social cognition
part 2 - social cognition
College 12 - Language
part 1 - language
part 2 - language
Samenvatting en Belangrijkste Begrippen
Perception & Attention
Learning and Memory
Cognitive Control
Emotion
Social Cognition
Language
Cognitive Neuropsychology 1
, College 2 - Perception & Attention
chapter 5 - sensation and perception
anatomy of the eye
light enters the surface through the cornea and activates the receptor cells of the retina located along the rear surface.
there are two types of receptor cells: rods and cones. the output of the receptor cells is processed in the middle layer of
the retina and then relayed to the central nervous system via the optic nerve, the axons of the ganglion cells.
the ventral and dorsal pathways: knowing what and where
the projections from V1 to higher areas in the cortex can be roughly divided into
two major parallel pathways: a ventral pathway leading from V1 to the temporal
lobe that is important for representing 'what' objects are (vision-for-action) and a
dorsal pathway leading from V1 to the parietal lobe that is important for
representing 'where' things are (vision-for-perception)
right/left eye blindness (1), bitemporal
hemianopia (2) and LVF hemianopia (6)
are the most important to know
lesion in the primary visual cortex (back of
the brain): patients might still respond to
stimuli in the blind field: blindsight
with cortical blindness, both sides of the
optic radiation nerves (5) are impaired
blindsight
blind subjects in a recent study responded (pupil response → fear is smaller and happy is larger) to images of happy or
fearful body postures and facial expressions - even though they were not aware of what they were seeing.
one area known to receive visual information independently of the visual cortex is the amygdala (brain's emotional
control center)
the visual cortex
V1 sends feedforward to many higher visual areas including areas such as V2, V3, V4 and motion sensitive area MT.
area V4 is especially important for color perception and some neurons in V4 respond well to more complex features or
combination of features.
the lateral occipital cortex (LOC) has a role in object recognition and responds strongly to a variety of shapes and objects
human neuroimaging studies have shown that there is a region in the fusiform gyrus, called the fusiform face area (FFA),
that responds more strongly to faces than to just about any other category of objects
Cognitive Neuropsychology 2
, the parahippocampal place area (PPA) is another strongly category-selective region that responds best to houses,
landmarks, and indoor and outdoor scenes. this area responds more weakly to other types of stimuli such as faces, bodies
or inanimate objects.
the middle-temporal (MT) area is important for motion perception. almost all neurons in area MT are direction-selective,
meaning that they respond selectively to a certain range of motion directions and not to others
motion perception
akinetopsia = motion blindness → you see everything moving in frame motions
motion is the interaction between 'where' and 'what'. you need a good working LOC and MT area to detect motion
correctly. with only MT everything is blurry and with only the 'what' stream (LOC) you see movement in frames but
when you put both together you get accurate motion perception → thus, MT and LOC cooperate by sharing information
experiment to identify regions involved in motion and color perception
in the color condition, the prominent activation was medial, in areas corresponding to human V4
in the motion condition, the activation was more lateral, in areas corresponding to human MT (V5)
both stimuli produced significant activation in primary visual cortex, when compared to a control condition in which
there was no visual stimulation
achromatopsia
people with achromatopsia have a damaged hue perception and see everything in black and white (complete
colorblindness)
patient with achromatopsia are bad at color matching and they show diminished sensitivity for illusory contour and
complex shapes
synesthesia
people with synesthesia see different colors for different letters and numbers, there are other cases of synesthesia but
about 70% has chromatic-graphemic synesthesia
chapter 6 - object recognition
the ventral 'what' path is most involved in object recognition
object recognition can be measured via the BOLD signal in the lateral occipital complex (LOC). in these measures,
animals motions or random motions were presented. the graph showed that activity was greater during the motion objects
than during the random motions.
object perception is extremely flexible, e.g. we can easily classify novel stimuli or recognize objects from various angles.
object recognition is presumably both viewpoint dependent and viewpoint independent
repetition suppression effect: when the same stimulus is shown twice, there is less activation in the brain
hierarchical coding hypothesis
at the lowest level of the hierarchy are edge detectors.
these feature units combine to form corner detectors,
which in turn combine to form cells that respond to even
more complex stimuli, such as surfaces.
Cognitive Neuropsychology 3
, a. the hypothesized computational stages for
hierarchical coding
b. a neural implementation of the computational stages
illustrated in part a
disadvantages:
final percept by a single cell (susceptible to errors or
sudden loss)
does not explain that we can perceive new objects
what if the properties of the objects change? (we can
still recognize the object)
ensamble coding hypothesis
objects are defined by the simultaneous activation of a set
of defining properties. e.g. 'granny' is recognized by the
co-occurrence of her glasses , face shape, hair color and
so on
advantages:
recognition due to not just one unit, but to collective
activation of many units; losing some units just
degrades recognition
novel objects are recognized due to activation of
units that represent familiar features
agrees with single cell recordings; cells in IT prefer
certain stimuli over others but are also activated by
other, visually similar, stimuli
visual agnosia
three types of visual agnosia
1. apperceptive agnosia
object recognition problems become more evident when a patient is asked to identify objects based on limited
stimulus information (line drawing or an unusual perspective)
unusual views test: in the unusual views test, subjects must judge whether two photographs taken from different
vantage points show the same object
shadows test: in the shadows test, subjects must identify the objects when seen under normal or shadowed
illumination. in both tests, patients with right-hemisphere lesions, especially in the posterior area, performed much
worse than did control subjects or patients with left-hemisphere lesions
Cognitive Neuropsychology 4
