Neural Plasticity
The brain's ability to reorganize its structure, function, and connections in response to experience, learning, injury, or environmental changes. Plasticity operates at multiple levels, from synaptic strengthening (long-term potentiation) to large-scale cortical remapping.
Example: London taxi drivers who memorize the city's complex street layout show measurably larger posterior hippocampi compared to bus drivers who follow fixed routes, demonstrating experience-dependent structural plasticity.
Working Memory
A limited-capacity cognitive system that temporarily holds and manipulates information needed for complex tasks such as reasoning, comprehension, and learning. Baddeley's model proposes a central executive, phonological loop, visuospatial sketchpad, and episodic buffer.
Example: When mentally calculating 47 times 3, you must hold the intermediate products in mind while performing each step of the multiplication, engaging the dorsolateral prefrontal cortex and posterior parietal cortex.
Hemispheric Lateralization
The tendency for certain cognitive functions to be processed predominantly by one cerebral hemisphere. While both hemispheres contribute to most tasks, specific functions show asymmetric organization, such as left-hemisphere dominance for language in most right-handed individuals.
Example: Split-brain patients, whose corpus callosum has been severed, demonstrate that the left hemisphere can name objects presented to the right visual field but the right hemisphere cannot verbally report objects shown to the left visual field.
The Default Mode Network
A large-scale brain network comprising the medial prefrontal cortex, posterior cingulate cortex, and angular gyrus that is most active during rest and internally directed thought. It is involved in mind-wandering, autobiographical memory retrieval, and social cognition.
Example: When a person lies in an fMRI scanner with no task to perform, the default mode network activates spontaneously, but it deactivates when the person begins a demanding external attention task like mental arithmetic.
Long-Term Potentiation (LTP)
A persistent strengthening of synaptic connections following repeated high-frequency stimulation, widely regarded as a cellular mechanism underlying learning and memory. LTP involves NMDA receptor activation, calcium influx, and subsequent changes in AMPA receptor density.
Example: In the hippocampus, when presynaptic and postsynaptic neurons fire together repeatedly, their synaptic connection strengthens, making future transmission more efficient -- a process summarized by the phrase 'neurons that fire together wire together.'
Executive Function
A set of top-down cognitive control processes mediated primarily by the prefrontal cortex that enable goal-directed behavior. Executive functions include inhibitory control, cognitive flexibility, and working memory updating.
Example: The Stroop task, in which participants must name the ink color of a color word (e.g., the word 'RED' printed in blue ink), requires inhibitory control to suppress the automatic reading response, engaging the anterior cingulate cortex and dorsolateral prefrontal cortex.
Mirror Neuron System
A network of neurons, originally discovered in the premotor cortex of macaque monkeys, that fire both when an individual performs an action and when they observe another individual performing the same action. In humans, a similar system is thought to support action understanding, imitation, and empathy.
Example: When you watch someone reach for a cup of coffee, premotor and parietal regions in your own brain activate as though you were performing the same grasping movement, potentially allowing you to understand the other person's intention.
Attention Networks
The brain organizes attention through at least three functionally distinct networks: the alerting network (maintaining vigilance, involving the locus coeruleus and right frontal cortex), the orienting network (directing attention to sensory stimuli, involving the superior parietal lobule and frontal eye fields), and the executive attention network (resolving conflict, involving the anterior cingulate cortex).
Example: When a driver hears a sudden horn blast, the alerting network raises arousal, the orienting network shifts spatial attention toward the sound source, and the executive network evaluates whether evasive action is needed.
