Chapter 2 Flashcards
define cognitive neuroscience
the study of the physiological basis of cognition
levels of analysis
the idea that a topic can be studied in many different ways, with each approach contributing its dimension to our understanding
levels of analysis when studying physiological cognition
we can study it at levels ranging from the whole brain to structures within the brain, to chemicals that create electrical signals within these structures.
action potential
- temporary reversal of a neuron’s interior polarity
- negative to positive charge
- the opening of voltage-sensitive sodium ion channels, allows positively charged sodium ions inside the neuron
- travel to the axon terminal buttons and trigger synaptic vesicles containing neurotransmitters to release the neurotransmitters across the synapse
nerve net
- a network of continuously interconnected nerve fibers (as contrasted with neural networks, in which fibers are connected by synapses)
- a complex pathway for conducting signals uninterrupted through the network
neuron doctrine
- the idea that individual cells transmit signals in the nervous system
- these cells are not continuous with other cells
cell body
the metabolic center of the neuron that contains mechanisms to keep the cell alive
dendrites
receive signals from other neurons
axon
- usually long processes that transmit signals to other neurons from the cell body to the synapse at the end of the axon
- Aka nerve fibres
synapse
space between the end of an axon and the cell body or dendrite and the next axon
neural circuits
group of interconnected neurons that are responsible for neural processing
resting potential
- inside the neuron has a charge of -70 mV
- at rest
nerve impulse
- neuron is stimulated and reverses the interior polarity of the neuron to 40 mV
- the reversal is action potential
microelectrodes
- a device that measures electrical signals
- small wires that record electrical signals from single neurons
- can measure action potential
- 2 points of reference
2 points of reference for microelectrodes
- inside the neuron: recording electrode
- outside the neuron: reference electrode
neurotransmitters
- chemical messengers that cross the synapse and bind to the dendrites of a nearby neuron
- e.g. GABA, endorphins, dopamine, etc
principle of neural representation
states that everything a person experiences is based on representations in the person’s nervous system
neuron firing
- many neurons at higher levels of the visual system fire to complex stimuli like geometrical patterns and faces
- a specific stimulus causes neural firing that is distributed across many areas of the cortex
- e.g. it was discovered that memory is not determined by a single “memory area,” because there are many areas involved in creating memories and remembering them later.
feature detectors - Hubel and Wiesel
- they called these neurons feature detectors because they responded to specific stimulus features such as orientation, movement, size and length
- each neuron in the visual area of the cortex responded to a specific type of stimulation presented to a small area of the retina.
what do neurons in the visual cortex respond to
neurons in the visual cortex respond to oriented bars
what do neurons in the temporal lobe respond to
- neurons in the temporal lobe respond to complex geometrical stimuli
- neurons in a different area of the temporal lobe also respond to faces
hierarchal processing
processing that occurs in progression from lower to higher areas of the brain
experience-dependent plasticity
- a mechanism that causes an organism’s neurons to develop so they respond best to the type of stimulation to which the organism has been exposed
- supports the idea that perception is determined by neurons that fire to specific qualities of a stimulus
sensory coding
refers to how neural firing represents various characteristics of the environment
specificity coding
- the representation of a specific stimulus by the firing of neurons that respond only to that stimulus
- the idea of specificity coding is straightforward but unlikely to be correct
- e.g. the signaling of a person’s face by the firing of a neuron that responds only to that person’s face
population coding
neural representation of a stimulus by the pattern of firing of a large number of neurons
sparse coding
neural coding based on the pattern of activity in small groups of neurons
neural networks
- are interconnected areas of the brain that can communicate with each other
- if many areas are involved in a particular type of cognition, that they might be connected
4 principles of neural networks
- there are complex structural pathways called networks that form the brain’s information highway
- within these structural pathways there are functional pathways that serve different functions
- these networks operate dynamically, mirroring the dynamic nature of cognition
- there is a resting state of brain activity, so parts of the brain are active all the time, even when there is no cognitive activity
structural connectivity
the brain’s “wiring diagram” created by nerve axons that connect different brain areas
track-weighted imaging (TWI)
- is based on detection of how water diffuses along the length of nerve fibers
- led to the coining of the term ‘connectome’
connector
- the structural description of the networks of elements and connections forming the human brain
- wiring diagram of neurons in the brain
functional connectivity
- is determined by the extent to which the neural activity in separate brain areas is correlated with each other
- if the responses of two brain areas are correlated with each other, this means that they are functionally connected
- saying two areas are functionally connected does not necessarily mean that they directly communicate by neural pathways
resting-state fMRI
- a response recorded when a person is at rest (not involved in any cognitive tasks)
- one method of determining whether the responding areas are correlated
default mode network (DMN)
- a network of structures that are active when a person is not involved in specific tasks
- areas in frontal and parietal lobes have been identified as part of the DMN
- one of the brains largest networks
localization of function
- specific functions are served by specific areas of the brain
- e.g. areas have been identified that are specialized to process information involved in the perception of movement, form, speech, and different aspects of memory.
cortical equipotentiality
- a popular idea in the early 1800s, that the brain operates as an indivisible whole, as opposed to operating based on specialized areas
cerebral cortex
- 3mm thick
- outer layer of the brain used for cognitive functions
- where higher level processing of sensory information occurs
- can be divided into 4 lobes
frontal lobe
- thinking
- problem-solving
- coordinate senses
- broca’s area: speech production
temporal lobe
- auditory cortex
- hearing
- fusiform face area
- processing of complex visual stimuli
- wernicke’s areas: speech comprehension
occipital lobe
- visual cortex
- vision
parietal lobe
- somatosensory cortex
- touch perception
- pressure
- pain
brocas aphasia
- condition associated with damage to Broca’s area, in the frontal lobe
- characterized by labored ungrammatical speech and difficulty in understanding some types of sentences
wernicke’s aphasia
- condition, caused by damage to Wernicke’s area, that is characterized by difficulty in understanding language, and fluent, grammatically correct, but incoherent speech.
- produce meaningless speech
- can’t understand others speech
- absence of normal grammar
prosopagnosia
- caused by damage to the temporal lobe that is characterized by an inability to recognize faces
- damage to the FFA
double dissociation
damage to one part of the brain that results in impaired function a and intact function b
fusiform face area (FFA)
processes faces and responds to face stimuli
parahippocampal place area (PPA)
is activated by places, outdoors, inside a room, but not by other stimuli
extrastriate body area (EBA)
is activated by bodies, arm, stick figures, shadows, but not other stimuli (like faces)
distributed representation
- activity in multiple areas of the brain is associated with a function
- occurs when a specific cognition activates many areas of the brain
- highlights a central principle of cognition, most of our experience is multidimensional
dynamics of cognition
- the flow of activity within and across the functional networks in the brain also changes, depending on conditions
- change between networks can be both rapid (like the cup example, rapidly switching and sharing information between functional networks) and slow (e.g. memory)
