#brain

• Abducens nerve — An anatomical and clinical term used to denote the sixth cranial nerve (abducens nerve or lateral rectus nerve), which exclusively innervates the lateral rectus muscle of the eye. In neurological semiology and clinical psychiatry, paralysis or impairment of the abducens nerve causes convergent strabism and diplopia (double vision), being a crucial indicator for diagnosing intracranial hypertension, brainstem tumors, or skull base fractures, phenomena often accompanied by acute mental confusion or organic delirium.
• Abduction — The movement by which a limb, a limb segment, or the eyeball is moved away from the median axis of the body or a reference line. In neurological semiology, testing abduction (such as ocular abduction, performed by cranial nerve VI) is essential for locating brainstem lesions. In clinical psychiatry, resistance to passive abduction of the limbs is analyzed as a marker for waxy flexibility or catalepsy in catatonic syndromes.
• Abkhaz (language) — The language spoken by the Abkhaz people, belonging to the Northwest Caucasian language family; as an adjective, it represents the feminine form of the word 'abhaz'. In neuropsychology and speech pathology (aphasiology), the highly complex grammatical structure of the Abkhaz language (characterized by a massive consonant inventory and polysynthetic verbal structure) has served as a clinical model for studying how the human brain processes difficult sounds after brain trauma or strokes.
• Acalculia — A clinical neurological or neuropsychological deficit characterized by the acquired loss of the ability to perform simple arithmetic operations or to understand fundamental mathematical concepts, typically occurring due to an organic brain injury (usually affecting the left parietal lobe). Unlike dyscalculia, which is a congenital developmental disorder, achalusia represents a cognitive impairment secondary to trauma, stroke, or neurodegenerative processes.
• Acataphasia — A severe neuropsychological speech disorder characterized by the patient's inability to formulate syntactically and grammatically correct sentences, whereas the ability to pronounce isolated words and the comprehension of their meaning remain intact. This symptom typically arises from focal brain lesions or specific neurodegenerative conditions, leading to fragmented, agrammatic, and incoherent expression.
• Achromatognosia — A rare neurological disorder (gnosic) characterized by the patient's inability to recognize, identify, or name colors, even though their peripheral visual system, retina, and optic nerve are structurally intact. This condition is usually caused by lesions located in the occipito-temporal cerebral cortex (associative visual area) and often manifests within visual agnosia.
• Acromiotonia — A pathophysiological condition characterized by a state of marked muscular hypertonia, rigidity, or persistent muscular contracture localized strictly within the body's extremities (hands and feet). This complex neuromuscular phenomenon reflects a structural disruption of myotatic reflexes, typically encountered in pyramidal or extrapyramidal disorders, brainstem lesions, or central motor-neuron disturbances.
• Aphasia — A severe communication disorder consisting of the total or partial loss of the ability to speak, write, and understand articulate or written language, occurring in the absence of sensory deficits or vocal apparatus impairment. It is triggered by acquired organic lesions in the cerebral cortex, primarily affecting the language-dominant hemisphere.
• Afferentation — A foundational physiological process consisting of the continuous transmission of nerve impulses and excitations from peripheral receptor neurons to the central nervous system neurons and cerebral cortex.
• Aphimia — A specific form of motor aphasia characterized by the loss of the ability to execute the articulated movements required for speech, while comprehension and the peripheral vocal apparatus remain intact. In clinical neurology, aphimia is caused by focal lesions in the left frontal lobe.
• Agnosia — A neurological disorder characterized by an inability to recognize or interpret sensory impressions, such as objects, persons, sounds, or shapes, despite intact primary sensory organs and general intellectual functioning; it typically results from structural damage to the associative cerebral cortex.
• Agraphia — A neurological disorder characterized by the partial or complete loss of the ability to write, resulting from acquired brain damage to the dominant hemisphere, unrelated to motor paralysis of the hand or general intellectual impairment.
• Agrammatism — A neurological language disorder commonly associated with Broca's aphasia, characterized by the loss of the ability to produce grammatically correct sentences; patients exhibit a telegraphic speech style, omitting functional words such as prepositions, articles, and conjunctions.
• Scatterbrained — Experiencing a state of delirium or manifesting a temporary mental confusion structurally induced by illness or fever; in current and figurative usage, it describes a scatterbrained, confused, or absent-minded person whose actions or words appear completely reckless, absurd, and disconnected from immediate reality. As a past participle, it represents the final state of the act of raving, being integrated alike into refined literature and Romanian folk dialects to portray a behavioral profile marked by eccentricity or microscopic disorganization.
• Scatterbrained — A scatterbrained, inattentive, or absent-minded person who acts without discernment or speaks without thinking; someone prone to blunders due to a lack of focus. As an adjective, it describes a fickle, superficial nature or a way of being characterized by confusion and random decisions.
• Hare-brained — Characterized by reckless, chaotic actions or thoughts that lack any logical or pragmatic foundation; a manner of expression typical of a scatterbrained person, defined by sterile fantasies, structural incoherence, and a complete disconnection from objective reality. The term applies to projects, ideas, or theories conceived without prior analysis and inherently doomed to organizational failure.
• Scatterbrained — Having temporarily or permanently lost the ability to focus, being absent-minded, scatterbrained, dazed, or lacking presence of mind; a person whose actions are incoherent due to fatigue, stress, or a natively disorganized nature. As a noun, it designates an individual prone to major confusions, who speaks nonsensically or acts completely randomly in daily life.
• Scatterbrained — The feminine form for a person who easily loses concentration, manifesting a state of confusion, inattention, or profound mental distraction; a woman characterized by scatterbrained behavior, prone to innocent daily blunders or decisions made under the impulse of the moment. As a qualifying adjective, it describes an action, attitude, or feminine nature marked by a lack of presence of mind and a temporary disconnection from practical details.
• Albuminorrhagia — The presence and quantitative concentration of albumin or total proteins in the cerebrospinal fluid (CSF); a diagnostic test used in neurology, whose increased value (hyperalbuminorrhagia) indicates an impairment of the blood-brain barrier.
• Alcmaeon — The standard Latinized form of the Greek name Alcmeon (Alkmaion); in history and philosophy, it refers to Alcmaeon of Croton (5th century BCE), a pre-Socratic philosopher and renowned medical theorist, considered among the first to perform anatomical dissections and propose the brain as the central seat of intelligence and perception. In mythology, he is one of the Epigoni, son of Amphiaraus and Eriphyle, who killed his mother to avenge his father.