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  • Executive function, the cognitive control of behavior, depends on the prefrontal cortex, which is extensively developed in higher primates and especially humans.

  • Working memory is a short-term, capacity-limited cognitive buffer that stores information and permits its manipulation to guide decision making and behavior.

  • Attention permits the selection of relevant information from the enormous welter of sensory inputs. Attention may be effortful or may result “bottom-up” from the appearance of a salient stimulus.

  • Attention depends on working memory and on mechanisms that filter sensory inputs for access to working memory.

  • Attention and working memory are modulated by drugs that directly or indirectly stimulate dopamine D1 receptors and noradrenergic receptors. Such drugs, most notably the psychostimulants methylphenidate and amphetamine, are used to treat attention deficit hyperactivity disorder (ADHD).

  • ADHD is strongly genetically determined, but it has not yet been possible to identify specific risk genes.

  • Obsessive–compulsive disorder (OCD) and Tourette syndrome may represent related abnormalities in the circuitry connecting the prefrontal cortex, striatum, and thalamus. Both are highly heritable conditions, although the specific genes involved remain unknown.

  • Declarative or explicit memory, which is the memory of facts and events, and nondeclarative or implicit memory, which includes all other forms such as procedural memory and habits, are the two broad categories of memory.

  • Structures in the medial temporal lobe, such as the hippocampus, are particularly important for the temporary storage of declarative memories.

  • The striatum plays a central role in procedural and habit memory.

  • The amygdala, part of the temporal lobe, and the nucleus accumbens, part of the ventral striatum, are important in emotional memory.

  • Long-lasting changes in synaptic efficacy (synaptic plasticity) are thought to be important mechanisms for storing memories.

  • Strong emotions enhance memory formation, likely because of the associated activation of diffusely projecting neurotransmitter systems (eg, monoamines, acetylcholine).

  • Despite intense interest in finding drugs that enhance memory under pathologic conditions (eg, Alzheimer disease) or normal conditions (eg, aging), no robustly effective agents have yet been developed.

  • Social cognition refers to cognitive and emotional processes that underlie social functioning, including social judgments and social affiliation.

  • Autism, one of the most strongly heritable neuropsychiatric illnesses, describes a spectrum of disorders characterized by abnormal social function, language impairments, restricted interests, and repetitive behaviors.


The simplest nervous systems sense survival-relevant stimuli in the environment and respond reflexively for self-defense, to obtain nourishment, and to reproduce. As organisms became more complex, an increasing number of neurons were interposed between sensory inputs and motor outputs, creating what has been called “the great intermediate net.” In the human nervous system, this net has reached remarkable levels of complexity, making possible diverse and subtle forms of cognition and behavioral control including many kinds of learning and memory, abstract thought, the creation of fiction, music, and visual art, and the ability to navigate flexibly in uncertain and changing social situations. For the sake of survival, humans retain simple reflexive responses ...

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