Glossary Flashcards
Acetylcholine
A very important neurotransmitter excreted by synapses. In the peripheral nervous system, it transduces action potentials in motorneurons into muscle action. In the brain itself, the release of acetylcholine, known as cholinergic transmission, acts both rapidly, to directly excite its postsynaptic targets, as well as more slowly, to up- or down-regulate their excitability. Increasing activity of cholinergic neurons correlates with increasing arousal levels (Figure 5.1).
Achromatopsia
A specific deficit in the perception of colors due to localized damage to parts of the fusiform gyrus (Section 8.2).
Action Potential
AU-or-none, pulse-like change in the electrical potential across the neuronal membrane, about 100 mV in amplitude and 0.5-1 msec in width. Action potentials, or spikes (also referred to as spiking discharge or firing activity) are the primary means of rapidly communicating specific information between neurons and from neurons to muscles (Section 2.3).
Activity Principle
A hypothesis according to which there will be one or more groups of neurons that explicitly represent the different attributes of every direct percept—seeing red, smelling wet moss, the feeling of initiating an action (see explicit coding; Figure 2.5).
Aftereffect
Prolonged exposure to a stimulus attribute causes a shortlived deficit in the ability to detect that attribute (as in the orientation-dependent aftereffect; Section 6.2). In some cases, the opposite attribute is seen, as in the motion aftereffect where the observer sees upward motion after being habituated to downward motion (also known as the waterfall illusion; Section 8.3) or in color afterimages. Aftereffects are thought to be caused by a recalibration or adaptation of the underlying neurons.
Akinetopsia
A specific deficit in the perception of visual motion due to a cortical lesion in and around area MT (Section 8.3).
Anterior Cingulate Cortex (ACC)
Part of the central executive in the frontal lobe that may be key to the NCC (front-end pages; Section 7.6). It is made up of Brodmann’s areas 24, 25, 32, and 33 (Figure 7.1). The ACC monitors complex behaviors and is particularly active during cognitive conflicts and errors.
40 Hz Oscillations
See Oscillations
Arousal or Gating System
A set of upper brainstem (mesencephalic reticular formation; Figure 5.1), hypothalamic and midline thalamic structures (iNTRALAMiNAR NUCLEI and reticular nuclei) that mediate arousal states (wakefiilness and sleep). Bilateral damage to these causes coma. A functioning arousal system is a necessary condition for any conscious content to occur. Its neuronal correlates are part of the NCQ (Section 5.1).
Attention
The ability to concentrate on a particular stimulus, event, or thought while excluding competing ones. Selective attention is necessary for most forms of conscious perception. Two broad forms of selective attention can be distinguished, top-down and bottom-up attention (Chapter 9).
Attentional Searchlight
See top-down attention.
Driving Connections
See Strong Connections
Extinction
See Neglect.
Gamma Oscillations
See Oscillations
Ipsilateral
See Contralateral.
