Neurocognition Cognitive Neuroscience/neuropsychology n All cognition is the result of neurological activity –most closely linked to cerebral cortex The study of the relationships between neuroscience and cognitive psychology, especially those theories of the mind dealing with memory, sensation and perception, problem solving, language processing, motor functions and cognition

The relationship between brain and cognition n Cognition is a product of the brain. n Understanding the brain and its organization is useful for assessing the plausibility of cognitive theories

neural basis of cognition n can be considered at two levels of description… a) neuronal - one or a small collection of individual neurons b) neural systems - a large number of neurons that serve a similar function (localization of function); usually referred to by a collective name (e.g., cortex, temporal lobe, etc.)

Major regions of cerebral cortex n frontal lobes - motor activity, planning & moving, processing of affective info., spoken language (Broca' s area) n temporal lobes - audition, language perception (Wernicke' s area) n parietal lobes - somatosensation, spatial perception n occipital lobes - vision

Brain & Cerebral Cortex

Topographical organization n one-to-one correspondence between a point or location in an external system, such as the retina, and a point or location in the brain – e.g., motor cortex, occipital lobes

Neurons - Structure n Basic building block of nervous system –soma - cell body; contact site for other neurons – dendrites - contact site for other neurons – axon - conducts action potential away from cell body & dendrites towards other neurons – terminal buttons - at end of axon; site of connection to other neurons – myelin sheath - electrical insulation (optional)

neuronal functioning n Action potential - how neurons convey information; an electrochemical transmission along length of neuron n Synapse - site of “connection” between adjacent neurons or between neurons and muscle fibers –Terminal buttons of presynaptic dendrites/soma of postsynaptic neuron (or muscle fibres)

neurotransmitter n Transmitter substance - chemical produced by a neuron that enables it to affect an adjacent neuron or group of muscle fibres – Excitatory synapse - increases likelihood of AP in post-synaptic neuron –Inhibitory synapse - decreases likelihood of AP in post-synaptic neuron

neural representation of information n each neuron is connected to many other neurons (1:1000) n representation of information is due to the pattern of activation across many neurons (i.e., a concept or idea does not correspond to a single neuron) –permanent memories are coded by long-term synaptic changes (rate of presynaptic NT release, re-uptake, & postsynaptic dendritic sensitivity)

Compartmentalization vs. Mass Action n Phrenology - exact location specific, measured by bumps on the head n Compartmentalization - some functions,m such as motor activitiy, are associated with a specific area of the brain n Aggregate Field Theory - functions also distributed in other brain areas Currently believed it is a little of both

Anatomy of Brain n Review Structures of Forebrain, Midbrain and Hindbrain n Contralateral actions n Karl Lashley - localization vs. generalization of function research –theory of mass action n Current Models of neural processing?

Now... n Field of Neuroscience given big boost by development of techniques that allow us to peer into the human brain and reveal structures and processes never seen before. n The mostly noninvasive tools are possible due to advances in computer technology and brain scanning techniques

Then... n Excising of tissue n Electrical probes n EEG recordings n postmortem exams

Magnetic Resonance Imaging n a method of scanning the brain that produces detailed maps of brain structure without X-rays or other radiation by relying on the difference in the magnetic resonance of certain atomic nuclei.

MRI n body surrounded by electromagnets that align the nuclei of hydrongen atoms found in water. n Since hydrogen reflects water content, can infer varying densities of tissue n Good for static measures, but not for rapidly changing cognitive functions

Functional MRI (fMRI) n New method, capable of high-resolution images of functional activity in the brain n scan in 30 milliseconds n giant magnet surrounds the subject's head –Changes in the direction of the magnetic field induce hydrogen atoms in the brain to emit radio signals. These signals increase when the level of blood oxygen goes up, indicating which parts of the brain are most active.

CAT Scans n Computerized Axial Tomography n X-ray machine rotates around skull, sending tons of thin, fan-shaped x-ray beams that are recorded on detectors on the opposite side of their source n used to display cognitive structures

PET n Positron Emission Tomography n a type of scan that measures changes in blood flow associated with brain function by detecting positrons, positively charged particles emitted by radioactively labeled substances that have been injected into the body.

PET n Left - Subject Reading words n Right - Subject hearing Words

PET n Since brain activity involves an increase in blood flow, more blood—and radioactive substance—streamed into the areas of the volunteers' brains that were most active while they saw or heard words. n High costs, time for image recording is too long (20 seconds)

fMRI vs. PET n BOTH: blood flow to brain provides the signals detected –when resting neurons become active, blood flow to them increases n fMRI - detects changes in oxygen levels, which rise in nearby blood vessels when they are at rest n PET - relies on increased delivery of injected radioactive water, which diffuses out of the vessels to reach rest of brain

Next Generation of Scans... n Messages from the senses travel so swiftly through the brain that imaging machines such as PET and fMRI can’t really keep up with them. n To track these messages in real time, scientists now use faster methods - electrical recording techniques such as MEG (magnetoencephalography) or EEG (electroencephalography).

MEG and EEG n MEG - a technique for recording electrical signals from the brain based on changes in magnetic fields. n EEG - the recording of brain waves by means of electrodes attached to the skull.

Next Generation of Scans... n These techniques rely on large arrays of sensors or electrodes that are placed harmlessly on the scalp to record the firing of brain cells almost instantaneously. Their data may then be combined with anatomical information obtained by structural MRI scans.