Ch. 2: The Neural Basis for Cognition

Action potential

A brief change in the electrical potential of an axon. The action potential is the physical basis of the signal sent from one end of a neuron to the other; it usually triggers a further (chemical) signal to other neurons

Agnosia

A disturbance in a person’s ability to identify familiar objects

All-or-none law

The principle stating that a neuron or detector either fires completely or does not fire at all; no intermediate responses are possible. (Graded responses are possible, however, by virtue of the fact that a neuron or detector can fire more or less frequently, and for a longer or shorter time).

Amygdala

An almond-shaped structure in the limbic system that plays a central role in emotion and in the evaluation of stimuli

Aphasia

A disruption to language capacities, often caused by brain damage. See also fluent aphasia and nonfluent aphasia

Apraxia

A disturbance in the capacity to initiate or organize voluntary action, often caused by brain damage

Association cortex

The traditional name for the portion of the human cortex outside the motor and sensory projection areas

Axon

The part of a neuron that typically transmits a signal away from the neuron’s cell body and carries the signal to another location

Cell body

The area of a biological cell containing the nucleus and the metabolic machinery that sustains the cell

Central fissure

The separation dividing the frontal lobes on each side of the brain from the parietal lobes

Cerebellum

The largest area of the hindbrain, crucial for the coordination of bodily movements and balance

Cerebral hemisphere

One of the two hemispherical brain structures—one on the left side, one on the right—that constitue the major part of the forebrain in mammals

Coding

The system through which one type of information stands for, or represents, a different type of information. In the context of the nervous system, this term refers to the way in which activity in neurons manages to stand for, or represent, particular ideas or thoughts

Commisure

One of the thick bundles of fibers along which information is sent back and forth between two cerebral hemispheres

Computerized axial tomography (CT scan)

A neuroimaging technique that uses X-rays to construct a precise three-dimensional image of the brain’s anatomy

Contralateral control

A pattern in which the left half of the brain controls the right half of the body, and the right half of the brain controls the left half of the body

Convolutions

The wrinkles visible in the cerebral cortex that allow the enormouse surface area of the human brain to fit into the relatively small volume of the skull

Corpus callosum

The larges of the commissures linking the left and right cerebral hemispheres

Cortex

The outermost surface of an organ in the body’ psychologists are most commonly interested in the brain’s cortex and, specifically, the cerebral cortex

Dendrites

The part of a neuron that usually detects the incoming signal

Electroencephalogram (EEG)

A recording of voltage changes occurring at the scalp that reflect activity in the brain underneath

Event-related potentials

Changes in an EEG in the brief period just before, during, and after an explicitly defined event, usually measured by averaging together many trials in which this event has occurred

Forebrain

One of the three main structures (along with the hindbrain and midbrain) of the brain; the forebrain plays a crucial role in supporting intellectual functioning

Frontal lobes

The lobe of the brain in each cerebral hemisphere that includes the prefrontal area and the primary motor projection area

Functional magnetic resonance imaging (fMRI scan)

A neuroimaging technique that uses magnetic fields to construct a detailed three-dimensional representation of the activity levels in different areas of the brain at a particular moment in time

Fusiform face area (FFA)

A brain area apparently specialized for the perception of faces

Glia

A type of cell found (along with neurons) in the central nervous system. Glial cells have many functions, including the support of neurons, the repair of neural connections in case of damage, and a key role in guiding the initial development of neural connections. A specialized type of glia also provide electrical insulation for some neurons, allowing much faster transmission of neuronal signals

Hindbrain

One of the three main structures (along with the forebrain and the midbrain) of the brain; the hindbrain sits atop the spinal cord and includes several structures crucial for controlling key life functions

Hippocampus

A structure in the temporal lobe that is involved in the creation of long-term memories and spatial memory

Hypothalamus

A small structure at the base of the forebrain that plays a vital role in the control of motivated behaviors such as eating, drinking, and s*xual activity

Lateral fissure

The separation dividing the frontal lobes on each side of the brain from the temporal lobes

Lesion

A specific area of tissue damage

Limbic system

A set of brain structures including the amygdala, hippocampus, and parts of the thalamus. The limbic system is believed to be involved in the control of emotional behavior and motivation, and it also plays a key role in learning and memory

Localization of function

The research endeavor of determining what specific job is performed by a particular region of the brain

Longitudinal fissure

The separation dividing the brain’s left cerebral hemisphere from the right

Magnetic resonance imaging (MRI scan)

A neuroimaging technique that uses magnetic fields (created by radio waves) to construct a detailed three-dimensional representation of brain tissue. Like CT scans, MRI scans reveal the brain’s anatomy, but they are much more precise than CT scans

Midbrain

One of the three main structures (along with the forebrain and the hindbrain) of the brain; the midbrain plays an important role in coordinating movements, and it contains structures that serve as “relay” stations for information arriving from the sensory organs

Myelin sheath

The layer of tissue, formed by specialized glial cells, that provides insulation around the axons of many neurons. There are however, gaps in this insulation, and the neuronal signal essentially has to “jump” from one gap to the next, dramatically increasing the speed of neurotransmission

Neuroimaging techniques

Non-invasive methods for examining either the structure or the activation pattern within a living brain

Neurotransmitter

One of the chemicals released by neurons to stimulate adjacent neurons. See also synapse

Occipital lobes

The rearmost lobe in each cerebral hemisphere, and the one that includes the primary visual projection area

Parietal lobes

The lobe in each cerebral hemisphere that lies between the occipital and frontal lobes and that includes some of the primary sensory projection areas, as well as circuits that are cruicial for the control of attention

Positron emission tomography (PET scan)

A neuroimaging technique that determines how much glucose (the brain’s fuel) is being used by specific areas of the brain at a particular moment in time

Postsynaptic membrane

The cell membrane of the neuron “receiving” information across the synapse. Often contrasted with presynaptic membrane

Prefrontal cortex

The outer surface (cortex) of the frontmost part of the brain (i.e., the frontmost part of the frontal lobe). The prefrontal cortex has many functions but is crucial for the planning of complex or novel behaviors, so this brain area is often mentioned as one of the main sites underlying the brain’s executive functions

Presynaptic membrane

The cell membrane of the neuron “sending” information across the synapse. Often contrased with postsynaptic membrane

Primary motor projection area

The strip of tissue, located at the rear of the frontal lobe, that is the departure point for nerve cells that send their signals to lower portions of the brain and spinal cord, and that ultimately result in muscle movement

Primary sensory projection area

The main point of arrival in the cortex for information arriving from the eyes, ears, and other sense organs

Subcortical structures

Identified pieces of the brain that are underneath the cortex and therefore are hidden from view in drawings of an intact brain. These structures include the thalamus, the hypothalamus, and the various components of the limbic system

Synapse

The area that includes the presynaptic membrane of one neuron, the postsynaptic membrane of another neuron, and the tiny gap bewteen them. The presynaptic membrane releases a small amount of neurotransmitter that drifts across the gap and stimulates the postsynaptic membrane

Temporal lobes

The lobe of the cortex lying inward and down from the temples. The temporal lobe in each cerebral hemisphere includes the primary auditory projection area, Wernicke’s area, and, subcortically, the amygdala and hippocampus

Thalamus

A part of the lower portion of the forebrain that serves as a major relay and integration center for sensory information

Threshold

The activity level at which a cell or detector responds, or fires

Transcranial magnetic stimulation (TMS)

A technique in which a series of strong magnetic pulses at a specific location on the scalp causes temporary disruption in the brain region directly underneath this scalp area

Unilateral neglect syndrome

A pattern of symptoms in which affected individiuals ignore all inputs coming from one side of space. Individuals with this syndrome put only one of their arms into their jackets, eat food from only half of their plates, read only half of words and so on