Localization of Brain Function

Abstract

Localization of brain function is the goal of cognitive neuroscience, behavioral neurology, and clinical neuroanatomy. Its armamentarium relies on connectional methods (diffusion tensor imaging), correlational methods (e.g., magnetic resonance imaging, functional magnetic resonance imaging, voxel-based morphometry, positron emission tomography), lesion models (e.g., traumatic brain injuries), and stimulation methods (e.g., transcranial magnetic stimulation). Theories of brain function include holistic, localizationist, and associationist models.

Localization of brain function is described following the various cerebral lobes, i.e., frontal lobe (with the primary motor cortex, supplementary motor area, premotor cortex, prefrontal cortex, and orbitofrontal area of the frontal pole), parietal lobe (with primary somatosensory cortex, secondary somatosensory cortex, somatosensory association area, postcentral gyrus, superior and inferior parietal lobules, supramarginal and angular gyri, angular gyrus, and cuneus), occipital lobe (with primary visual cortex, visual association cortex, mesial and lateral aspect), temporal lobe (with primary auditory cortex, auditory association cortex, inferomedial aspect of the amygdala and hippocampus, anterior tip including amygdala; bilateral lesions, latero-inferior aspect, latero-superior aspect, and regions with epileptogenic lesions).

Language areas include Wernicke’s area and Broca’s area.

Cortical syndromes are grouped in right (non-dominant) hemisphere syndromes (i.e., constructional apraxia, dressing apraxia, neglect and denial, and color blindness), dominant (left) hemisphere syndromes (i.e., ideomotor apraxia, visual agnosia, alexia without agraphia, Gerstmann’s syndrome, and color agnosia), and bi-hemispheric syndromes (i.e., ideational apraxia and Anton syndrome). Aphasias include global aphasia, Broca’s aphasia, Wernicke’s aphasia, conduction aphasia, transcortical sensory aphasia, and transcortical motor aphasia.

The limbic system, with its various regions, plays important functions: hippocampus (recent memory, modulation of emotions), amygdala (olfaction, emotive behavior, integration of autonomic visceral activity), stria terminalis (autonomic response to fear, rage, and other emotions), septal nuclei (pleasure center of the brain), and cingulate cortex (cortical regulation of basic autonomic functions, behavior, and emotional modulation of pain).

Corpus callosum disconnection syndromes are described.

Basal ganglia are involved in the regulation of motor function, initiation and coordination of motor activities, and cognitive functioning

The thalamus as an important relay station is, when lesioned, responsible for sensory disturbances, motor disturbances, disturbances of alertness, mood and affect, memory, visual disturbances, autonomic disturbances, disturbances of complex sensorimotor functions and executive functions. The hypothalamus regulates functions of metabolism, body temperature, sleep, and emotional behavior.

The cerebellum is functionally concerned with the coordination of locomotion, the control of muscle tone, and the regulation of equilibrium.

White matter tracts and its involvement in normal function and dysfunction can be considered as the perisylvian white matter, the early visual pathways white matter, the white matter of the ventral and dorsal visual pathways matter, and the white matter of extended visual pathways matter.