PS244 cognitive neuroscience
multi-cell recordings (multi-unit recordings)
- the electrical activity (in terms of action potentials per second) of many individually recorded neurons recorded at one or more electrodes
cognitive neuropsychology
the study of brain-damaged patients to understand normal cognition
"active" region in fMRI scan
(all neurons needs oxygen to be alive) - measure the physiological response of a region in a task that is greater relative to some other condition
amygdala
A limbic system structure involved in memory and emotion, particularly in the detection of fearful and threatening stimuli.
P400-600
- -sensitive to the repetition and familiarity of specific person identities, in terms of names and faces
mesocortex
- In between the neocortex and the allocortex. Involved in cognitive control, motivation and emotional response - including the cingulate gyrus and insula
hemodynamic methods
- PET & fMRI & fNIRS - measures a downstream consequence of neural activity
olfactory bulbs
- lie on the under-surface of the frontal lobes - connections to the limbic system underscore the importance of smell for detecting environmentally salient stimuli and its influence on mood and memory
additive factors method
- a general method for dividing reaction times into different stages - developed by Sternberg - advantage: one can take an unknown factor and determine whether this has an interactive effect on stimulus perceptibility or whether it has an interactive effect with the number of items in the array or both
grandmother cell
- a hypothetical neuron that just responds to one particular stimulus (e.g., the sight of one's grandmother) - including voice, thought, sight, etc.
thalamus
- a major component of the subcortex - consists of two interconnected egg-shaped masses that lie in the center of the brain and appear prominent in a medial section - the main sensory relay for all senses (except smell) between the sense organs (eyes, ears, etc.) and the cortex. - at the posterior end of the thalamus lie the lateral geniculate nucleus and the medial geniculate nucleus, which are the main sensory relays to the primary visual and primary auditory cortices, respectively.
N170
- a negative peak at 170ms - strongest over right posterior temporal electrode sites - active no matter the face is famous or not, as well as for smiley cartoon faces - the activity is weaker if the face is degraded
magnetoencephalography (MEG)
- a noninvasive method for recording magnetic fields generated by the brain at the scalp - prefaced by "m/M"
limbic system
- a region of subcortex involved in relating the organism to its present and past environment - involved in the detection and expression of emotional responses
reference point of EEG
- a site that is relatively uninfluenced by the variable under investigation - to gain the EEG measure by comparing the voltage between two or more different sites - a common one is the mastoid bone behind the ears or a nasal reference, or the average of all electrodes
fNIRS (functional near-infrared spectroscopy)
- allows neuroimaging of brain activation by tracking blood flow via changes in hemoglobin - hemodynamic method - measures BOLD signals -sends "light" of a particular wavelength to the brain (800 nm); uninfluenced by the bone and skin but scattered by the oxy- and deoxyhemoglobin - more portable and more tolerant of movement than fMRI - cheaper - can be used to image shallow activity that is close to the scalp
the link between the relative amount of oscillation (the "power") in different bands to different kinds of cognitive function
- alpha band --> increased attention (filtering out irrelevant information), when attending to internal images - gamma band --> perpetual integration of parts into wholes (objection recognition, binding or grouping) - not a one-to-one relationship!
dipole modeling
- an attempt to solve the inverse problem in ERP research that involves assuming how many dipoles (regions of electrical activity) contribute to the signal recorded at the scalp
different stages in the additive factor method
- assume that a task can be divided into different stages and the reaction time for each stage is measured, and each stage is distinctive and separate from the other 1. encoding the probe digit 2. comparing the probe digit with the items held in memory 3. deciding which response to make 4. responding by executing the button press
the main structure of basal ganglia
- caudate nucleus: an elongated tail-like structure - putamen: lying more laterally - globus pallidus (lying more medially)
computerized tomography (CT)
- constructed according to the amount of X-ray absorption in different types of tissue. - bone & skull: the most --> white - brain matter: the intermediate --> gray - cerebrospinal fluid: the least-->black - used in clinical settings, for diagnosis - can't distinguish between gray matter and white matter
disorder associated with basal ganglia
- disorders of this area can be characterized as hypokinetic (poverty of movement) or hyperkinetic (excess of movement), e.g. Parkinson's disease and Huntington's disease - also implicated in the learning of rewards, skills, and habits
four lobes of each hemisphere
- frontal, parietal, temporal, occipital
substantia nigra
- in midbrain - connected to the basal ganglia - associated with the symptoms of Parkinson's disease
basal ganglia
- large rounded masses that lie in each hemisphere - surround and overhang the thalamus in the center of the brain - involved in regulating motor activity, and the programming and termination of action
N250
- larger for famous and personally familiar faces relative to unfamiliar faces and respond to the presentation of different images of the same person - it codes properties of the specific face rather than the specific image
hypothalamus
- lies beneath the thalamus and consists of a variety of nuclei that are specialized for different functions primarily concerned with the body - include body temperature, hunger and thirst, sexual activity, and regulation of endocrine functions - tumors in this area can lead to eating and drinking disorders, precocious puberty, dwarfism and gigantism
single-cell recordings
- measure the responsiveness of a neuron to a given stimulus (in terms of action potentials per second) - invasive, impossible to be noninvasive (e.g. on the scalp) because the signal is too weak and there are noises from other neurons. - normally on experimental animals, and occasionally on human brain during brain surgery - can be intracellular or extracellular - measure the action potential of a single cell when the stimulus is present, "spikes" per second/ firing rate/ spiking rate
electroencephalography (EEG)
- measurements of electrical signals generated by the brain through electrodes placed on different point on the scalp - useful for measuring the relative timing of cognitive events and neural activity - noninvasive and involves recording (not stimulating) - Attention! EEG is not best equipped for detecting the location of neural activity!
structural imaging
- measures of the spatial configuration of different types of tissue in the brain (principally CT and MRI). - based on the fact that different types of tissue have different physical properties - the different properties --> static maps of the physical structure of the brain - computerized tomography (CT) - magnetic resonance imaging (MRI)
functional imaging
- measures temporary changes in brain physiology associated with cognitive processing; the most common method is fMRI and is based on a hemodynamic measure - assume that neural activity produces local physiological changes in that region of the brain - produce dynamic maps of the moment-to-moment activity of the brain when engaged in cognitive tasks
position emission tomography (PET)
- measures the change in blood flow to a brain region directly -require administration of a radioactive tracer -hemodynamic method
cerebellum
- part of hindbrain - literally 'little brain' - consists of highly convoluted folds of gray matter - organized into two interconnected lobes - important for dexterity and smooth execution of movement
medulla oblongata
- part of hindbrain - regulates vital functions such as breathing, swallowing, heart rate and the wake-sleep cycle.
inferior colliculi
- part of the midbrain - gray matter nuclei - specialized for auditory processing
superior colliculi
- part of the midbrain -gray matter nuclei - integrate information from several senses (visual, hearing, and touch) in programming fast eye movements
pros of MEG over EEG
- permits a much better spatial resolution in addition to the excellent temporal resolution - signal unaffected by skull, meninges, etc. - more sensitive to activity at sulci
cons of MEG vs EEG
- poor at detecting deep dipoles - expensive and limited availability
representation
- properties of the world that are manifested in cognitive systems (mental representation) and neural systems (neural representation) - physical properties (e.g. sound, shape) and abstract forms of knowledge (e.g. religions, factual knowledge) - the neural representation is not one-to-one relationship with mental representation
associative priming
- refers to the fact that reaction times are faster to a stimulus if that stimulus is preceded by a stimulus that tends to co-occur with it in the environment
gyri
- singular: gyrus - the raised folds of the cortex
sulci
- singular: sulcus - the buried grooves of the cortex
event-related potentials (ERPs)
- the average amount of change in voltage at the scalp that is linked to the timing of particular cognitive events (e.g. stimulus, response) - since activity of other non-related regions will also be detected, the signal-to-noise ratio is low in single trial - but it will be higher if averaging multiple trials of EEG - P = positive peaks - N = negative peaks P1 = the first positive peak P300 = a positive peak at 300 ms - positive or negative doesn't mean excitatory or inhibitory states!
inverse problem
- the difficulty of locating the sources of electrical activity from measurements taken at the scalp (in ERP research)
oscillation-based measures
- the rate of change of the EEG signal is linked to cognitive processes
temporal coding
- the synchrony of firing may be used by a population of neurons to code the same stimulus or event - may be one mechanism for integrating information across spatially separated populations of neurons.
reaction time
- the time taken between the onset of a stimulus/event and the production of a behavioral response (e.g., a button press). Also referred to as response time - not to measure the absolute timing for one process, but the relative timing (e.g. HoUSe vs HOUSE vs house)
disorders related to the cerebellum
- unilateral lesion leads to poor coordination on the same side of the body as the lesion - bilateral lesions result in a wide and staggering gait, slurred speech (dysarthria) and eyes moving in a to-and-fro motion (nystagmus).
oscillation
- wave-like structure - the EEG signal tends to oscillate at different rates/frequency bands - alpha waves reflect oscillations in the 7 to 14 Hz range - beta in 15 to 30 - gamma in 30 and above range - occurs because large groups of neurons tend to be in temporal synchrony with each other in terms of their firing (action potentials) and in terms of their slower dendritic potentials (which form the basis of the EEG signal).
pons
-part of hindbrain - a key link between the cerebellum and cerebrum - receive information from visual areas to control eye and body movements.
basic requirements of doing EEG
1. a whole population of neurons must be active in synchrony to generate a large enough electrical field 2. this population of neurons must be aligned in a parallel orientation so that they summate together rather than cancel out--> so the signals in the thalamus can't be detected
four ways to divide the cerebral cortex
1. by the pattern of gyri and sulci 2. by cytoarchitecture: Brodmann's areas 3. by function 4. by connectivity
the advantages of ERP over reaction time
1. have an excellent temporal resolution 2. provides a continuous measurement of changes over time 3. it is possible to link this to neural processes in the brain 4. enables electrophysiological changes associated with unattended stimuli to be measured whereas a reaction-time measure always requires an overt behavioral response
sequence for acquiring an MRI scan
1. magnetic field of protons initially floating randomly in body 2. external magnetic field applied across the body part (e.g. the brain), hydrogen nuclei in water molecules becomes the detecting signal --> some protons aligned 3. brief radio wave pulse orients the protons to 90 degrees and produces a measurable MR signal 4. protons return back (or relax). New slices is scanned
ERP studies in face recognition
1. perceptual coding of the facial image 2. facial identity is computed 3. map the perceptual code onto a store of known faces and represent the face irrespective of viewing conditions 4. representation of the identity of the person that is not tied to any modality and may enable retrieval of other types of knowledge
the arrangement of the electrodes in EEG
10-20 system of Jasper - F = frontal - P = parietal - O = occipital - T = temporal - C = central even number for right hemisphere odd number for left hemisphere z for midline
fMRI
A technique for revealing blood flow and, therefore, brain activity by comparing successive MRI scans. - noninvasive - measure the active brain region or where the blood flows to during an event -hemodynamic method - amount of data: brain volumes
endogenous
ERP components that appear to depend on properties of the task (e.g., what the participant is required to do with the stimulus)./ the nature of the task - these can occur in the absence of an external stimulus
voxel
a volume-based unit; in imaging research the brain is divided into many thousands of these
neocortex
The outermost part of the cerebral cortex, making up 80 percent of the cortex in the human brain. - meaning "new cortex"
cognitive neuroscience
a bridging discipline between cognitive science and cognitive psychology, on the one hand, and biology and neuroscience, on the other
subcortex
a collection of gray matter nuclei beneath the cortical surface and the intervening white matter
sparse distributed representation
a distributed representation in which a small proportion of the neurons carry information about a stimulus/event
fractional anisotropy (FA)
a measure of the extent to which diffusion takes place in some directions more than others
dipole
a pair of positive and negative electrical charges separated by a small distance
voxel-based morphometry (VBM)
a technique for segregating and measuring differences in white matter and gray matter concentration
phrenology
a theory that individual differences in cognition can be mapped onto differences in skull shapes
cognitive subtraction
a type of experimental design in functional imaging in which activity in a control task is subtracted from activity in an experimental task - by comparing the activity of the brain in a task that utilizes a particular cognitive component to the activity of the brain in a baseline task that does not, it is possible to infer which regions are specialized for this particular cognitive component
cognition
a variety of higher mental processes such as thinking, perceiving, imagining, speaking, acting and planning.
magnetic resonance imaging (MRI)
advantages: 1. doesn't use ionizing radiation --> safe 2. provides a much better spatial resolution --> discern gyri 3. provides better discrimination between white matter and gray matter --> enable early diagnosis of some pathologies and study the association between brain and function 4. can be used for detecting the changes in blood oxygenation associated with neural activity (or fMRI)
fully distributed representation
all the information about a stimulus/event is carried in all the neurons of a given population
local representation
all the information about a stimulus/event is carried in one of the neurons
null event in fMRI
allow the BOLD signal to dip toward baseline, essentially providing the necessary variability in the signal needed for the analysis
limbic structures
amygdala, hippocampus, mamillary bodies, and cingulate cortex
T2* image
based on the distortion of the T2 component by deoxyhemoglobin
allocortex
brain tissue with three layers or unlayered organization - including the primary olfactory cortex and hippocampus
hemodynamic response function (HRF)
changes in the BOLD signal over time three phases: 1. initial dip 2. overcompensation 3. undershoot -relatively stable across sessions with the same participant in the same region - sluggish - but we can superimpose trials over trials (timing of stimulus presentation * hemodynamic response function = predicted fMRI data
exogenous (or evoked potentials)
components of ERP that appear to depend on the physical properties of a stimulus (e.g., sensory modality, size, intensity).
interactive effects
different factors affect the same processing stage
additive effect
if different factors affect different stages of processing, then the effects should have additive effects on the overall reaction time.
hippocampus
important for learning and memory
parts of cingulate cortex
involve in the detection of emotional and cognitive conflicts
Brodmann's areas
regions of cortex defined by the relative distribution of cell types across cortical layers (cytoarchitecture)
BOLD (blood oxygen-level-dependent contrast)
the signal measured in fMRI that relates to the concentration of deoxyhemoglobin in the blood
diencephalon
thalamus and hypothalamus
pure insertion (or pure deletion)
the assumption that adding an extra component does not affect the operation of earlier ones in the sequence
dualism
the belief that mind and brain are made up of different kinds of substance - René Descartes was one of the famous proponent of this idea - i.e. mind =/ brain
dual-aspect theory
the belief that mind and brain are two levels of description of the same thing - Spinoza supported this
reductionism
the belief that mind-based concepts will eventually be replaced by neuroscientific concepts i.e. mind = brain
ERP components/ deflection
the different peaks and troughs of the ERP signal
rate coding
the informational content of a neuron may be related to the number of action potentials per second
cortex
the outer layer of the cerebrum (the cerebral cortex), composed of folded gray matter and playing an important role in consciousness
mind-body problem
the problem of how a physical substance (the brain) can give rise to our sensations, thoughts and emotions (our mind)
mental chronometry
the study of the time-course of information processing in the human nervous system - the basic idea is that changes in the nature or efficiency of information processing will manifest themselves in the time it tales to complete a task.
tesla (T)
the unit of the strength of the magnetic field - typical scanner: 1.5-3 T - earth: 0.0001 T
mamillary bodies
two small round protrusions that have traditionally been implicated in memory
Peterson et al. (1988)
use cognitive subtraction to study the brain region for visual word recognition (CAKE / +), pronunciation producing(read "cake" / passive viewing), and semantic associate (see "cake" say "eat" / see "cake" say "cake")
diffusion tensor imaging(DTI)
uses MRI to measure white matter connectivity between brain regions
T1 relaxation time
variation in the rate at which the protons return back to the aligned state following the radio frequency pulse - to distinguish between different types of tissue - for structural images of the brain - gray matter --> gray - white matter --> white
T2 component
when in the misaligned state, at 90 degrees to the magnetic field, the MR signal decays because of local interactions with nearby molecules.