Summary for exam
1. General
The Neurobiology of Cognition is about the brain mechanisms responsible for
perception, attention, action, memory, language, reasoning, and consciousness.
− Cognitive processing differs from stimulus-response reflex systems in
several ways, notably neural representations. There are stages of
processing between stimulus input and response output reflecting
selection, thought, decision making and prior knowledge.
− Classical dissociations between distinct facets of cognition were based on
study of neurological patients with specific types of brain damage. Animal
studies have also played a key part as they offer the opportunity of
exacting invasive analyses. Challenge of developing effective models.
− Newer approaches include examining genetic differences (humans) or
creating transgenic and viral modifications (animals).
Retrieval for learning
• Repeated studying after learning had no effect on delayed recall but
repeated testing produced a large positive effect.
• Retrieval is critical for learning.
Speech and language
• Acquired effortlessly in first few years of life, rapidly learn the phonemic
boundaries, and develop implicit understanding of grammar. Second
language with great difficulty.
• Noam Chomsky- distinction between surface (syntax) and deep structure
(meaning) reflected by meaningless but comprehensible sentences.
• Major receptive and expressive speech areas: Broca’s area and
Wernicke’s area through study of specific neurological cases:
> Broca studied aphasic patients with brain injuries. Left ventroposterior
region of frontal lobe is essential from expressive speech.
> Wernicke’s aphasia is receptive form involving inability to comprehend
language. Speech retains natural rhythm and syntax. Caused by damage
to BA22, the posterior part of the superior temporal gyrus of the
dominant hemisphere.
> Broca and Wernicke’s areas are connected by the uncinate fasciculus.
• These findings contribute to concept of localization of function; specific
brain functions are carried out by diverse brain regions working together
in networks. Interactions are critical to the way cognition is performed.
, Levels of analysis
Sensation and perception
• Visual illusions: retinal bitmap (sensation) is interpreted in brain to
produce perception. For example:
> Extraction of lines and edges by V1 can result in ambiguity, Necker cube.
> Illusory contours reveal object-based nature of feature extraction.
• Evolution has led to information often being context specific, not all
contained within stimuli. Sensory and perceptual systems of the different
modalities have regional and circuit properties which make this possible.
• Motor output is also complex; response and action only latter has
intentionality. Responses have to be timed perfectly to be effective.
1) Auditory
• Barn owl encodes ongoing timing disparity (ITD) and coincidence
detectors (Jeffress) to work out in which direction prey is located hence
rotating head by a certain angle (bird aims to catch prey).
• Anatomical circuits hence convert the temporal difference into a place
signal, detected by neurons which fire. Seen in nucleus laminaris of barn
owl brain.
,2) Vision
• Visual pathway in humans is from retina to superior colliculus and lateral
geniculate nucleus.
• From SC to posterior parietal cortex. From LGN to primary visual cortex
and then dorsal stream (where) to PPC and ventral stream (what) to
infero-temporal cortex.
• Anatomical distinct regions for colour, motion and object identification:
--> Hubel and Wiesel columnar organisation of extraction of features:
> Extends through subsequent processing as far as inferotemporal cortex.
> Specialized modules, for example face is perceived in superior temporal
gyrus. Cells fire stronger in STG when face is presented.
--> Center surround organisation at level of LGN.
--> Edge detection in visual cortex.
--> Categorical organisation of features in inferotemporal cortex.
--> Coding in medial temporal lobe where images of common object/ name of
object evoke response. Implies abstract code beyond mere vision involving
memory is necessary.
• Boundary between discrete facets of brain function such as sensation and
perception and now memory is unclear. Same is seen in movement
domain where explicit sensory feedback is central to effective action
control.
3) Attention
• Receive much more sensory information than we can process in detail,
must attend selectively.
• Attention to one modality (hearing) or to information within one modality
(specific voice) is generally at the expense of ability to process other
information. Change blindness occurs when attention is so focused, we
fail to notice things.
• In visual modality, superior colliculus directs rapid eye movements to
bring retinal fovea onto object of attention.
• Attention can also be covert; in absence of eye movements, we can be
cognitively cued to attend to a specific region of an image before we have
time to move eyes to focus on it. Suggests something else at play.
• Attention can be to specific objects; particular features of image may pop
out or be object of deliberate search. Visual processing can hence be
biased by these processing systems (bottom up, top down) to prioritize
certain features or whole items of a visual object for attention and further
processing.
, • Single cell recordings in non-human primates shows rates of firing in visual
pathways to one object, or to another, can be measured with each object
alone, and are seen to be decreased to each object by the presence of the
other when the two are presented together – i.e., neural competition.
Reasoning and consciousness
• The capacity to reason creatively implies ability to “go beyond the
information given” (Jerome Bruner, Harvard), i.e. to put together
information given at different times in a manner that enables new
information to be worked out. A conscious process and perhaps uniquely
human.
Memory
• Not unitary faculty of mind nor located at single place. Multiple types of
memory.
• Short term memory and long-term memory -> declarative and non-
declarative forms. Distinction in terms of memory capacity, fidelity, and
active and passive nature of memory storage.
• Working memory mediated by frontal lobe, long term memory mediated
by medial temporal lobe, striatum, cerebellum.
• Identifying critical brain areas and networks then within and across these
the role of activity dependent synaptic plasticity in mediating memory.
Representation
• Brain activity is thought to represent the world around us. How does
nervous system construct and process these representations to perceive
and act within environment?
• David Marr three levels of understanding:
> Computational level – what the brain has to do
> Algorithmic level – mathematical description of how this happens (e.g.,
ITD to place code).
> Implementational level – neuronal circuits in brain.
• Different levels can reveal different answers. Harnessing multiple levels
of analysis from gene to molecule to neural circuit to whole brain allows
us to better understand physiological and molecular mechanisms in brain
to treat it.
1. General
The Neurobiology of Cognition is about the brain mechanisms responsible for
perception, attention, action, memory, language, reasoning, and consciousness.
− Cognitive processing differs from stimulus-response reflex systems in
several ways, notably neural representations. There are stages of
processing between stimulus input and response output reflecting
selection, thought, decision making and prior knowledge.
− Classical dissociations between distinct facets of cognition were based on
study of neurological patients with specific types of brain damage. Animal
studies have also played a key part as they offer the opportunity of
exacting invasive analyses. Challenge of developing effective models.
− Newer approaches include examining genetic differences (humans) or
creating transgenic and viral modifications (animals).
Retrieval for learning
• Repeated studying after learning had no effect on delayed recall but
repeated testing produced a large positive effect.
• Retrieval is critical for learning.
Speech and language
• Acquired effortlessly in first few years of life, rapidly learn the phonemic
boundaries, and develop implicit understanding of grammar. Second
language with great difficulty.
• Noam Chomsky- distinction between surface (syntax) and deep structure
(meaning) reflected by meaningless but comprehensible sentences.
• Major receptive and expressive speech areas: Broca’s area and
Wernicke’s area through study of specific neurological cases:
> Broca studied aphasic patients with brain injuries. Left ventroposterior
region of frontal lobe is essential from expressive speech.
> Wernicke’s aphasia is receptive form involving inability to comprehend
language. Speech retains natural rhythm and syntax. Caused by damage
to BA22, the posterior part of the superior temporal gyrus of the
dominant hemisphere.
> Broca and Wernicke’s areas are connected by the uncinate fasciculus.
• These findings contribute to concept of localization of function; specific
brain functions are carried out by diverse brain regions working together
in networks. Interactions are critical to the way cognition is performed.
, Levels of analysis
Sensation and perception
• Visual illusions: retinal bitmap (sensation) is interpreted in brain to
produce perception. For example:
> Extraction of lines and edges by V1 can result in ambiguity, Necker cube.
> Illusory contours reveal object-based nature of feature extraction.
• Evolution has led to information often being context specific, not all
contained within stimuli. Sensory and perceptual systems of the different
modalities have regional and circuit properties which make this possible.
• Motor output is also complex; response and action only latter has
intentionality. Responses have to be timed perfectly to be effective.
1) Auditory
• Barn owl encodes ongoing timing disparity (ITD) and coincidence
detectors (Jeffress) to work out in which direction prey is located hence
rotating head by a certain angle (bird aims to catch prey).
• Anatomical circuits hence convert the temporal difference into a place
signal, detected by neurons which fire. Seen in nucleus laminaris of barn
owl brain.
,2) Vision
• Visual pathway in humans is from retina to superior colliculus and lateral
geniculate nucleus.
• From SC to posterior parietal cortex. From LGN to primary visual cortex
and then dorsal stream (where) to PPC and ventral stream (what) to
infero-temporal cortex.
• Anatomical distinct regions for colour, motion and object identification:
--> Hubel and Wiesel columnar organisation of extraction of features:
> Extends through subsequent processing as far as inferotemporal cortex.
> Specialized modules, for example face is perceived in superior temporal
gyrus. Cells fire stronger in STG when face is presented.
--> Center surround organisation at level of LGN.
--> Edge detection in visual cortex.
--> Categorical organisation of features in inferotemporal cortex.
--> Coding in medial temporal lobe where images of common object/ name of
object evoke response. Implies abstract code beyond mere vision involving
memory is necessary.
• Boundary between discrete facets of brain function such as sensation and
perception and now memory is unclear. Same is seen in movement
domain where explicit sensory feedback is central to effective action
control.
3) Attention
• Receive much more sensory information than we can process in detail,
must attend selectively.
• Attention to one modality (hearing) or to information within one modality
(specific voice) is generally at the expense of ability to process other
information. Change blindness occurs when attention is so focused, we
fail to notice things.
• In visual modality, superior colliculus directs rapid eye movements to
bring retinal fovea onto object of attention.
• Attention can also be covert; in absence of eye movements, we can be
cognitively cued to attend to a specific region of an image before we have
time to move eyes to focus on it. Suggests something else at play.
• Attention can be to specific objects; particular features of image may pop
out or be object of deliberate search. Visual processing can hence be
biased by these processing systems (bottom up, top down) to prioritize
certain features or whole items of a visual object for attention and further
processing.
, • Single cell recordings in non-human primates shows rates of firing in visual
pathways to one object, or to another, can be measured with each object
alone, and are seen to be decreased to each object by the presence of the
other when the two are presented together – i.e., neural competition.
Reasoning and consciousness
• The capacity to reason creatively implies ability to “go beyond the
information given” (Jerome Bruner, Harvard), i.e. to put together
information given at different times in a manner that enables new
information to be worked out. A conscious process and perhaps uniquely
human.
Memory
• Not unitary faculty of mind nor located at single place. Multiple types of
memory.
• Short term memory and long-term memory -> declarative and non-
declarative forms. Distinction in terms of memory capacity, fidelity, and
active and passive nature of memory storage.
• Working memory mediated by frontal lobe, long term memory mediated
by medial temporal lobe, striatum, cerebellum.
• Identifying critical brain areas and networks then within and across these
the role of activity dependent synaptic plasticity in mediating memory.
Representation
• Brain activity is thought to represent the world around us. How does
nervous system construct and process these representations to perceive
and act within environment?
• David Marr three levels of understanding:
> Computational level – what the brain has to do
> Algorithmic level – mathematical description of how this happens (e.g.,
ITD to place code).
> Implementational level – neuronal circuits in brain.
• Different levels can reveal different answers. Harnessing multiple levels
of analysis from gene to molecule to neural circuit to whole brain allows
us to better understand physiological and molecular mechanisms in brain
to treat it.
