Ch.2- The Brain Flashcards
The Neural Substrate
hardware that allows cognitive processes to run. Understand how brain supports cognition and how cognitive processes unfold in the brain. Neural activity correlates with some cognitive operation, suggests this region of the brain is responsible for that function. There’s no simple mapping between regions of the brain and mental operations: brain not made up of clearly separable parts. Activity distributed over networks of brain regions during a single task (eg:listening)
OPERA Hypothesis
Patel(2011) specifies why musical training would benefit speech perception.
Overlap: brain networks used to process acoustic features of both speech and music
Precision: music vs speech places higher demands on these networks. Conveying structure of musical sequences requires more detailed information than conveying semantic content. Context based cues reduces degree of precision necessary in speech (top-down information)
OPERA Hypothesis :ERA
Emotion: positive emotional reward of performance
Repition: extensive practice
Attention: more “brain real estate” used for processing acoustic features.
Networds that process acoustic features function at higher levels of precision than needed for speech and communication.
Assertions in Neuroscience: You love your iPhone. Literally (Lidstrom,2011)
Experiment on if iphone causes feelings of love in brain. “But most striking of all was the flurry of activation in the insular cortex of the brain, which is associated with feelings of love”.
Insular cortex activity frequent in other experiments that have nothing to do with love- can also occur with feelings of disgust.
Very difficult to connect structure with function.
Localization of Function: Phrenology
Faculty psychology: Franz Gall (1758-1828)
Mental abilities are independent and autonomous functions. Could think of as precursor to modular varieties information processing approach.
Fodor(1983): innate modules that carry out functions
Phrenology: Gall’s student, Johan Spurzheim. Psychological strengths and weaknesses could be precisely correlated to the relative sizes of different brain areas.
Phrenology discredited: Size of brain region does not necessarily correspond to relative power. Different faculties not independent.
Localization of Function: Damage to Brain
Effects of brain damage in certain areas on functions: Case of Phineas Gage (1848): Accidental explosion drove railway spike through head, survived 12 years with most functions intact. Drastic personality changes noted (very impulsive)
Portion of the brain traversed was for several reasons, the best fitted to sustain the injury.
Aphasia
Language disruption caused by brain damage. Autopsies of patients with certain language impairments revelaved damage to regions of the brain.
Broca’s Aphasia
Motor/expressive
Good comprehension but halting or absent speech
Broca’s area is located above the auditory cortex and beside the prefrontal cortex
Wernicke’s Aphasia
Sensory/receptive
Fluent but nonsensical speech and difficulty comprehending language.
Wernicke’s area is located beside the auditory cortex
Challenging Localization
Other researchers found variation among individuals in location used for a given function (ie expressing and receiving language.
Divide between comprehension and production unclear. Most with expressive aphasia have some impairment with comprehension as well and vice versa.
Higher-order cognitive processes are complicated and interconnected-not localized in any one region, but distributed over a network.
Brains show some degree of plasticity following injury- healthy regions of brain may take over functions of damaged regions
Brain Lateralization
Cerebral hemispheres have different functions.
Left hemisphere usually dominant for language
Right hemisphere is dominant in processing auditory and visual information. They interact to process information and carry out cognitive processes.
Connected vby a bundle of neural fibers called the Corpus Callosum
Studies of Split-Brained Patients
Patients with severed corpus callosum. “The disruption of interhemispheric integration produces remarkably little disturbane in ordinary behaviour (Sperry).
Patient grasps familiar object that is obscured with left hand. The right hemisphere receives information. Although the patient could pick out the sunglasses from a set of objects, he could not name the object.
Techniques for studying the brain
Noninvasive techniques to examine functioning of normal brain.
Aim for basic understanding of brain imaging techniques and electrical recording methods.
Magnetic Resonance Imaging (MRI)
Like CAT (computerized axial tomography) scans, shows scans of “slices” of brain. MRI allows for clearer images, no exposure to radiation.
Uses magnetic field and radio waves to create images of organs and tissues. Static pictures of the brain
Functional MRI
Mapping between physical activity in the brain and its functional state. If 2 experimental conditions result in different patterns of neural activity they use different cognitive processes. Does not give information about time course of activity.
Hemodynamic changes: reflect changes in blood oxygen levels, direction of blood flow. Infer that brain regions with higher levels of blood flow or blood oxygen are more active.
Hemodynamic changes per small cubic section of the brain called a voxel.
Interpreting fMRI Signal
Assumptions: hemodynamic measurements reflect brain activity. Consistent changes in blood flow following stimulus reflect recruitment of brain areas to process stimulus.
Experimental control conditions critical: several areas of the brain will show activity, some not related to cognitive process of interest. Make control and experimental conditions as similar as possible, except for stimulus of interest.
Mind multiple comparisons: fMRI measures brain activity in small cubic regions called voxels. Can have many separate comparisons between voxels. False positives need to be adjusted for statistically, compare only relevant regions of the brain.
“In need a full length Atlantic Salmon For Science”
Bennet et al(2010) Neural Correlates of Interspecies Perspective taking in the post-mortem atlantic salmon.
fMRI scans on salmon shown pictures of social inclusive (vs exclusive situations)
false positive results by chance from making multiple comparisons (no correction applied)
Authors noted that between 25-40% of published studies using MRI did not correct for multiple comparisons
Electroencephalography
(EEG) measures postsynaptic potentials over a large number of neurons. Changes in electrical voltage as a result of neurotransmitters.
Continuous measure of brain activity-great temporal resolution but not spatial resolution. Examine timing of brain’s response to stimulus
Event-Related Potentials (ERP)
EEG waveforms lined up with onset of a stimulus (word)
Predictable parts or components that are thought to reflect certain cognitive processes. eg: greater P3 (N400) for semantically surprising information.
Transcranial Magnetic Stimulation (TMS)
Magnetic coil creates a magnetic field which produces an electrical current. Activate or inhibit specific brain circuits.
