Aphasia is an inability to comprehend or formulate language because of damage to specific brain regions. The major causes are stroke and head trauma;prevalence is hard to determine but aphasia due to stroke is estimated to be 0.1–0.4% in the Global North. Aphasia can also be the result of brain tumors,brain infections,or neurodegenerative diseases.
Expressive aphasia,also known as Broca's aphasia,is a type of aphasia characterized by partial loss of the ability to produce language,although comprehension generally remains intact. A person with expressive aphasia will exhibit effortful speech. Speech generally includes important content words but leaves out function words that have more grammatical significance than physical meaning,such as prepositions and articles. This is known as "telegraphic speech". The person's intended message may still be understood,but their sentence will not be grammatically correct. In very severe forms of expressive aphasia,a person may only speak using single word utterances. Typically,comprehension is mildly to moderately impaired in expressive aphasia due to difficulty understanding complex grammar.
Neurology is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the brain,the spinal cord and the peripheral nerves. Neurological practice relies heavily on the field of neuroscience,the scientific study of the nervous system.
Wernicke's aphasia,also known as receptive aphasia,sensory aphasia or posterior aphasia,is a type of aphasia in which individuals have difficulty understanding written and spoken language. Patients with Wernicke's aphasia demonstrate fluent speech,which is characterized by typical speech rate,intact syntactic abilities and effortless speech output. Writing often reflects speech in that it tends to lack content or meaning. In most cases,motor deficits do not occur in individuals with Wernicke's aphasia. Therefore,they may produce a large amount of speech without much meaning. Individuals with Wernicke's aphasia are typically unaware of their errors in speech and do not realize their speech may lack meaning. They typically remain unaware of even their most profound language deficits.
Apraxia is a motor disorder caused by damage to the brain,which causes difficulty with motor planning to perform tasks or movements. The nature of the damage determines the disorder's severity,and the absence of sensory loss or paralysis helps to explain the level of difficulty. Children may be born with apraxia;its cause is unknown,and symptoms are usually noticed in the early stages of development. Apraxia occurring later in life,known as acquired apraxia,is typically caused by traumatic brain injury,stroke,dementia,Alzheimer's disease,brain tumor,or other neurodegenerative disorders. The multiple types of apraxia are categorized by the specific ability and/or body part affected.
The following outline is provided as an overview of and topical guide to neuroscience:
Anosognosia is a condition in which a person with a disability is cognitively unaware of having it due to an underlying physical or psychological condition. Anosognosia can result from physiological damage to brain structures,typically to the parietal lobe or a diffuse lesion on the fronto-temporal-parietal area in the right hemisphere,and is thus a neuropsychiatric disorder. A deficit of self-awareness,it was first named by the neurologist Joseph Babinski in 1914. Phenomenologically,anosognosia has similarities to denial,which is a psychological defense mechanism;attempts have been made at a unified explanation. Anosognosia is sometimes accompanied by asomatognosia,a form of neglect in which patients deny ownership of body parts such as their limbs. The term is from Ancient Greek ἀ- a-,'without',νόσοςnosos,'disease' and γνῶσιςgnōsis,'knowledge'. It is also considered a disorder that makes the treatment of the patient more difficult,since it may affect negatively the therapeutic relationship.
Global aphasia is a severe form of nonfluent aphasia,caused by damage to the left side of the brain,that affects receptive and expressive language skills as well as auditory and visual comprehension. Acquired impairments of communicative abilities are present across all language modalities,impacting language production,comprehension,and repetition. Patients with global aphasia may be able to verbalize a few short utterances and use non-word neologisms,but their overall production ability is limited. Their ability to repeat words,utterances,or phrases is also affected. Due to the preservation of the right hemisphere,an individual with global aphasia may still be able to express themselves through facial expressions,gestures,and intonation. This type of aphasia often results from a large lesion of the left perisylvian cortex. The lesion is caused by an occlusion of the left middle cerebral artery and is associated with damage to Broca's area,Wernicke's area,and insular regions which are associated with aspects of language.
Neuroplasticity,also known as neural plasticity,or brain plasticity,is the ability of neural networks in the brain to change through growth and reorganization. It is when the brain is rewired to function in some way that differs from how it previously functioned. These changes range from individual neuron pathways making new connections,to systematic adjustments like cortical remapping. Examples of neuroplasticity include circuit and network changes that result from learning a new ability,environmental influences,practice,and psychological stress.
Transcortical motor aphasia (TMoA),also known as commissural dysphasia or white matter dysphasia,results from damage in the anterior superior frontal lobe of the language-dominant hemisphere. This damage is typically due to cerebrovascular accident (CVA). TMoA is generally characterized by reduced speech output,which is a result of dysfunction of the affected region of the brain. The left hemisphere is usually responsible for performing language functions,although left-handed individuals have been shown to perform language functions using either their left or right hemisphere depending on the individual. The anterior frontal lobes of the language-dominant hemisphere are essential for initiating and maintaining speech. Because of this,individuals with TMoA often present with difficulty in speech maintenance and initiation.
Behavioral neurology is a subspecialty of neurology that studies the impact of neurological damage and disease upon behavior,memory,and cognition,and the treatment thereof. Two fields associated with behavioral neurology are neuropsychiatry and neuropsychology. In the United States,'Behavioral Neurology &Neuropsychiatry' has been recognized as a single subspecialty by the United Council for Neurologic Subspecialties (UCNS) since 2004.
Norman Geschwind was a pioneering American behavioral neurologist,best known for his exploration of behavioral neurology through disconnection models based on lesion analysis.
Kenneth M. Heilman is an American behavioral neurologist He is considered one of the fathers of modern-day behavioral neurology.
Neurorehabilitation is a complex medical process which aims to aid recovery from a nervous system injury,and to minimize and/or compensate for any functional alterations resulting from it.
Arno Villringer is a Director at the Department of Neurology at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig,Germany;Director of the Department of Cognitive Neurology at University of Leipzig Medical Center;and Academic Director of the Berlin School of Mind and Brain and the Mind&Brain Institute,Berlin. He holds a full professorship at University of Leipzig and an honorary professorship at Charité,Humboldt-Universität zu Berlin. From July 2022 to June 2025 he is the Chairperson of the Human Sciences Section of the Max Planck Society.
Bruce H. Dobkin is an American Professor of Neurology at the David Geffen School of Medicine at UCLA,medical director of the UCLA Neurologic Rehabilitation and Research Program,and Co-Director of the UCLA Stroke Center. He serves as editor-in-chief of Neurorehabilitation and Neural Repair.
Steven L. Small is the Aage and Margareta Møller Distinguished Professor in Behavioral and Brain Sciences at the University of Texas at Dallas,and dean of its School of Behavioral and Brain Sciences. Small is a specialist in the neurobiology of language.
Roy Hamilton is professor in the departments of Neurology,Psychiatry,and Physical Medicine and Rehabilitation at University of Pennsylvania (Penn). He is the Director of Penn's Laboratory for Cognition and Neural Stimulation (LCNS),and launched the Brain Stimulation,Translation,Innovation,and Modulation Center (brainSTIM) at the University of Pennsylvania in 2020.
Friedhelm Christoph Hummel is a German neuroscientist and neurologist. A full professor at École Polytechnique Fédérale de Lausanne,he is the Defitech Chair of Clinical Neuroengineering,and the head of the Hummel Laboratory at EPFL's School of Life Sciences. He also is an associate professor of clinical neuroscience at the University of Geneva.
