One of two nuclei of the oculomotor nerve. The main oculomotor nucleus is located in the anterior part of the gray matter surrounding the cerebral aqueduct of the midbrain at the level of the superior colliculus. It consists of a cluster neurons that supply all extrinsic muscles of the eye, with the exception of the …
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Odds ratio
The odds of a given outcome (= p/q, where p is the proportion with the outcome and q is the proportion without the outcome) for participants with a particular characteristic, divided by the odds of that outcome for participants without the characteristic (or with one unit less of the characteristic). Helpful outlines of how the …
Ocular dominance columns
Segregation of the inputs from the right and left eyes into columns that form alternating bands in the primary visual cortex. Today a ‘column’ is understood to be cells in any vertical cluster that share the same tuning for any particular for any given receptive field attribute. More broadly speaking, a ‘column’ refers to periodic …
Occipital cortex (or lobe)
At the back of each cerebral hemisphere, it is separated from the parietal and temporal lobes by two imaginary line from the top of the parieto-occipital sulcus to the pre-occipital notch (an indentation in the base of each cerebral hemisphere) on its lateral surface, and on the medial surface by the parieto-occipital sulcus. The surface area …
Ockham’s (or Occam’s) razor
A form of methodological reductionism, it is the scientific mandate originating with William of Ockham (1285-1349), sometimes referred to as the ‘parsimony of postulates’, and summarised with the acronym KISS (‘keep it simple, stupid’). It contains the idea, fundamental to the scientific method, that one should not make more assumptions than the minimum needed or, …
Occipital-temporal pathway
Connections between the occipital lobe (involved in vision) and temporal lobe (involved in visual cognition). Long-standing anatomical evidence led to conclusion that there are direct fiber connections between the two lobes via the inferior longitudinal fasciculus. More recent evidence in humans and monkeys suggests otherwise: connections between the two regions are both indirect involving a …
Observational learning
Learning that results from observing the behaviour of others. Also referred to as modeling, shaping, vicarious reinforcement and social learning. The latter term is associated with the work of Albert Bandura and in particular his famous Bobo doll experiment in which aggressive behavior was acquired by children observing it others. Shaping is perhaps not an …
Obsessive-compulsive disorder (OCD)
A type of anxiety disorder dominated by obsessions and compulsions usually with child or adolescent onset, and which often occur with a high probability and rigid manner, even at the expense of more adaptive patterns of action. Symptoms of OCD can range from mild to severe. In its mild form, individuals may spend part of …
Obligation
Feelings and judgments that a course of action is necessary based on considerations of what is right and wrong. This description approximates the meaning of a moral obligation. In most societies, a moral obligation constitutes a duty that a person has based on such considerations, but which is not necessarily legally binding. An allied concept …
Object segregation
The ability to identify an object as a bounded whole separate from its background, supporting surfaces, and other objects. This ability appears to have been achieved unambiguously by 8 months of age in typically developing infants. See Object identity, Object unity