Neuropsychology
Topics Brain regions Clinical neuropsychology Cognitive neuropsychology Cognitive neuroscience Dementia Human brain Neuroanatomy Neurophysiology Neuropsychological assessment Neuropsychological rehabilitation Traumatic brain injury
Brain functions Arousal Attention Consciousness Decision making Executive functions Natural language Learning Memory Motor coordination Perception Planning Problem solving Thought
People Alan Baddeley Arthur L. Benton David Bohm Antonio Damasio Phineas Gage Norman Geschwind Elkhonon Goldberg Patricia Goldman-Rakic Donald O. Hebb Kenneth Heilman Eric Kandel Edith Kaplan Muriel Lezak Benjamin Libet Rodolfo Llinás Alexander Luria Brenda Milner Karl H. Pribram Pasko Rakic Oliver Sacks Mark Rosenzweig Roger W. Sperry Hans-Lukas Teuber Henry Molaison ("H.M.", patient) K.C. (patient)
Tests Benton Visual Retention Test Continuous Performance Task Halstead-Reitan Neuropsychological Battery Hayling and Brixton tests Lexical Decision Task Luria-Nebraska neuropsychological battery Mini–mental state examination Rey–Osterrieth complex figure Stroop Test Wechsler Adult Intelligence Scale Wechsler Memory Scale Wisconsin Card Sorting Task
Psychology portal Philosophy portal Medicine portal
v t e

In neuropsychology, dissociation involves identifying the neural substrate of a particular brain function through identification of case studies, neuroimaging, or neuropsychological testing.

When dissecting complex mental tasks into their subcomponents, a researcher can establish a "single dissociation" between functions. This is done by demonstrating that a lesion to brain structure A disrupts function X but not function Y. Such a demonstration allows one to infer that function X and function Y are independent of each other in some way.^{[citation needed]}

Dr. Oliver Sacks has described many famous cases of dissociation in his books. Patient D.F., for example, was unable to place a card in a slot, but could do so when told to place it "as if mailing a letter". From this the conclusion was drawn that judging orientation is one ability (which D.F. had lost) and visual control of an action another (which D.F. could still do).^[1]

To strengthen a single dissociation, a researcher can establish a "double dissociation", a term that was introduced by Hans-Lukas Teuber in 1955.^[2] This is the demonstration that two experimental manipulations each have different effects on two dependent variables; if one manipulation affects the first variable and not the second, the other manipulation affects the second variable and not the first.^[3] If one can demonstrate that a lesion in brain structure A impairs function X but not Y, and further demonstrate that a lesion to brain structure B impairs function Y but spares function X, one can make more specific inferences about brain function and function localization.^[4]

In cognitive neuroscience, double dissociation is an experimental technique by which two areas of neocortex are functionally dissociated by two behavioral tests, each test being affected by a lesion in one zone and not the other.^[5] In a series of patients with traumatic brain injury, one might find two patients, A and B. Patient A has difficulty performing cognitive tests for, say auditory memory but has no problem with visual memory. Patient B has the opposite problem. By using neuroimaging (or neuropathology post-mortem) to identify the overlap and dissociation between lesioned areas of the brain, one can infer something about the localization of visual and auditory function in the normal brain.^[6]

Establishing a single dissociation between two functions provides limited and potentially misleading information, whereas a double dissociation can conclusively demonstrate that the two functions are localized in different areas of the brain.

To make the difference between single and double dissociations easier to understand, Parkin^[7] gives the following example:

If your TV set suddenly loses the color you can conclude that picture transmission and color information must be separate processes (single dissociation: they cannot be independent because you cannot lose the picture and still have the color). If on the other hand you have two TV sets, one without sound and one without a picture you can conclude that these must be two independent functions (double dissociation).

Paul Broca and Carl Wernicke were two physicians of the 1800s whose patients were evidence of the double dissociation between generating language (speech) and understanding language. Broca's patients could no longer speak but could understand language (non-fluent aphasia) while Wernicke's patients could no longer understand language but could produce jumbled speech (fluent aphasia). Post-mortems revealed lesions in separate areas of the brain in each case (now referred to as Broca's area and Wernicke's area respectively). Although the neurophysiology of language is now known to be more complicated than described by Broca or Wernicke, this classic double dissociation acted to begin modern neuropsychological investigation of language.^[8]

The conditions Capgras delusion and prosopagnosia have also been argued to represent a double dissociation. In the former, a patient is able to recognise a person but does not get the feeling of knowing them.^[9] In the latter, a patient is unable to recognise a familiar person but sometimes has a feeling of knowing.^[10]

v t e Psychology
History Philosophy Portal Psychologist
Basic psychology	Abnormal Affective neuroscience Affective science Behavioral genetics Behavioral neuroscience Behaviorism Cognitive/Cognitivism Cognitive neuroscience Social Comparative Cross-cultural Cultural Developmental Differential Ecological Evolutionary Experimental Gestalt Intelligence Mathematical Moral Neuropsychology Perception Personality Psycholinguistics Psychophysiology Quantitative Social Theoretical
Applied psychology	Anomalistic Applied behavior analysis Assessment Clinical Coaching Community Consumer Counseling Critical Educational Ergonomics Feminist Forensic Health Humanistic Industrial and organizational Legal Media Medical Military Music Occupational health Pastoral Political Positive Psychometrics Psychotherapy Religion School Sport and exercise Suicidology Systems Traffic
Methodologies	Animal testing Archival research Behavior epigenetics Case study Content analysis Experiments Human subject research Interviews Neuroimaging Observation Psychophysics Qualitative research Quantitative research Self-report inventory Statistical surveys
Concepts	Behavior Behavioral engineering Behavioral genetics Behavioral neuroscience Cognition Competence Consciousness Consumer behavior Emotions Feelings Human factors and ergonomics Intelligence Mind Psychology of religion Psychometrics
Psychologists	Wilhelm Wundt William James Ivan Pavlov Sigmund Freud Edward Thorndike Carl Jung John B. Watson Clark L. Hull Kurt Lewin Jean Piaget Gordon Allport J. P. Guilford Carl Rogers Erik Erikson B. F. Skinner Donald O. Hebb Ernest Hilgard Harry Harlow Raymond Cattell Abraham Maslow Neal E. Miller Jerome Bruner Donald T. Campbell Hans Eysenck Herbert A. Simon David McClelland Leon Festinger George A. Miller Richard Lazarus Stanley Schachter Robert Zajonc Albert Bandura Roger Brown Endel Tulving Lawrence Kohlberg Noam Chomsky Ulric Neisser Jerome Kagan Walter Mischel Elliot Aronson Daniel Kahneman Paul Ekman Michael Posner Amos Tversky Bruce McEwen Larry Squire Richard E. Nisbett Martin Seligman Ed Diener Shelley E. Taylor John Anderson Ronald C. Kessler Joseph E. LeDoux Richard Davidson Susan Fiske Roy Baumeister
Lists	Counseling topics Disciplines Organizations Outline Psychologists Psychotherapies Research methods Schools of thought Timeline Topics
Wiktionary definition Wiktionary category Wikisource Wikimedia Commons Wikiquote Wikinews Wikibooks

v t e Neuroscience
Outline History
Basic science	Behavioral epigenetics Behavioral genetics Brain mapping Brain-reading Cellular neuroscience Computational neuroscience Connectomics Imaging genetics Integrative neuroscience Molecular neuroscience Neural decoding Neural engineering Neuroanatomy Neurobiology Neurochemistry Neuroendocrinology Neurogenetics Neuroinformatics Neurometrics Neuromorphology Neurophysics Neurophysiology Systems neuroscience
Clinical neuroscience	Behavioral neurology Clinical neurophysiology Epileptology Neurocardiology Neuroepidemiology Neurogastroenterology Neuroimmunology Neurointensive care Neurology Neuro-oncology Neuro-ophthalmology Neuropathology Neuropharmacology Neuroprosthetics Neuropsychiatry Neuroradiology Neurorehabilitation Neurosurgery Neurotology Neurovirology Nutritional neuroscience Psychiatry
Cognitive neuroscience	Affective neuroscience Behavioral neuroscience Chronobiology Molecular cellular cognition Motor control Neurolinguistics Neuropsychology Sensory neuroscience Social cognitive neuroscience
Interdisciplinary fields	Consumer neuroscience Cultural neuroscience Educational neuroscience Evolutionary neuroscience Global neurosurgery Neuroanthropology Neural engineering Neurobiotics Neurocriminology Neuroeconomics Neuroepistemology Neuroesthetics Neuroethics Neuroethology Neurohistory Neurolaw Neuromarketing Neuromorphic engineering Neurophenomenology Neurophilosophy Neuropolitics Neurorobotics Neurotheology Paleoneurobiology Social neuroscience
Concepts	Brain–computer interface Development of the nervous system Neural network (artificial) Neural network (biological) Detection theory Intraoperative neurophysiological monitoring Neurochip Neurodegenerative disease Neurodevelopmental disorder Neurodiversity Neurogenesis Neuroimaging Neuroimmune system Neuromanagement Neuromodulation Neuroplasticity Neurotechnology Neurotoxin Self-awareness
Category Commons