From: http://www.waiting.com/glossarya.html and Neuroscience on the Web Series (NWS)
Acalculia - The inability to perform simple problems of arithmetic.
Agnosia - Failure to recognize familiar objects although sensory mechanism is intact. May occur for any sensory modality.
Lack of sensory recognition as the result of a lesion in the sensory association areas or association pathways of the brain. An example is looking at a common object but not recognizing it, nor associating meaning with the image. (The Neuroscience on the Web Series)
Agraphia - Inability to express thoughts in writing. Specifically, acquired disturbance of writing due to brain injury.
Alexia - Inability to read. Specifically, acquired disturbance of reading due to brain injury.
Alexia with Agraphia: difficulties with reading and writing; may be the result of damage to the angular gyrus in the hemisphere dominant for speech and language.
Amnesia - Lack of memory about events occurring during a particular period of time. See also: anterograde amnesia, retrograde amnesia, post-traumatic amnesia.
Amygdala: A structure which is attached to the tail of the caudate nucleus; it is considered to be a part of the limbic system and is involved in emotion.
Angular gyrus: The gyrus that lies near the superior edge of the temporal lobe, and immediately posterior to the supramarginal gyrus; it is involved in the recognition of visual symbols (Geschwind referred to it as the ``association cortex for association cortices'' and ``the most important cortical areas of speech and language''). Lesions in this area can result in alexia and agraphia.
Anomia - Inability to recall the names of objects. Persons with this problem often can speak fluently but have to use other words to describe familiar objects.
Anomia may be the result of damage to the angular gyrus in the hemisphere dominant for speech and language. (It is not a very reliably localised syndrome - all patients with Aphasia experience some problems with word finding.)
Anosmia - Loss of the sense of smell; may be a result of a lesion on the olfactory pathway.
Anterior commissure: One of the three major groups of commissural fibers; part of the Circle of Willis, the anterior commissure connects the temporal lobes, as well as connecting the temporal lobe to the amygdala and to the opposite occipital lobe; it is also connected to the corpus callosum.
Anterograde Amnesia - Inability to consolidate information about ongoing events. Difficulty with new learning.
Aphasia - Loss of the ability to express oneself and/or to understand language. Caused by damage to brain cells rather than deficits in speech or hearing organs or paralysis or incoordination of the musculature of speech or writing, or poor vision, or hearing.
Aphasia can affect auditory comprehension, oral expression, reading and writing. (Also includes sign language deficits?)
Aphasia, Expressive - Inability to find or formulate the words to express oneself even though knowing what one wants to say.
Aphasia, Fluent - Characterized by spontaneous use of language at normal speed that conveys little meaning.
Aphasia, Global - Severely limited residual ability to communicate with others. Includes both expressive and receptive aphasia.
Aphasia, Non-fluent - Characterized by awkward articulation, limited vocabulary, hesitant, slow speech output, restricted use of grammatical forms and a relative preservation of auditory comprehension.
Aphasia, Receptive - Problems in understanding what others attempt to communicate.
Aphasia, Subclinical - Refers to evidence of impaired linguistic processing on testing, which is not obvious in casual interactions with the person.
Aphemia - The isolated loss of the ability to articulate words without loss of the ability to write or comprehend spoken language.
Apraxia - Inability to carry out a complex or skilled movement; not due to paralysis, sensory changes, or deficiencies in understanding.
Apraxia, Constructional - Inability to assemble, build, draw, or copy accurately; not due to apraxia of single movements.
Apraxia, Ideomotor - Deficit in the execution of a movement due to inability to access the instructions to muscles stored by previous motor experience.
Apraxia of speech is an articulation (speech) disorder that results from brain damage. The deficit is in higher cortical functioning - these same muscles may function normally in reflex and automatic acts. Probably the part of the brain that generates the motor programs for speech/ phonology is damaged.
Arcuate fasciculus - The groups of fibers that connect Broca's area with Wernicke's area (these fibers connect to the angular gyrus) and are located below the supramarginal gyrus. According to Geschwind, damage to this area results in Conduction Aphasia.
Ataxia - A problem of muscle coordination not due to apraxia, weakness, rigidity, spasticity or sensory loss. Caused by lesion of the cerebellum or basal ganglia. Can interfere with a person's ability to walk, talk, eat, and to perform other self care tasks.