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Biomedical subjects

S Grossberg

Publications and source records attributed to S Grossberg.

At least 91 records · Page 5Linked to original sources
PubMed1984

A neural theory of circadian rhythms: Aschoff's rule in diurnal and nocturnal mammals.

A neural model of the suprachiasmatic nuclei suggests how behavioral activity, rest, and circadian period depend on light intensity in diurnal and nocturnal mammals. These properties are traced to the action of light input (external zeitgeber) and an activity-mediated fatigue signal (internal zeitgeber) on the circadian pacemaker. Light enhances activity of the diurnal model and suppresses activity of the nocturnal model. Fatigue suppresses activity in both diurnal and nocturnal models. The asymmetrical action of light and fatigue in diurnal vs. nocturnal models explains the more consistent adherence of nocturnal mammals to Aschoff's rule, the consistent adherence of both diurnal and nocturnal mammals to the circadian rule, and the tendency of nocturnal mammals to lose circadian rhythmicity at lower light levels than diurnal mammals. The fatigue signal is related to the sleep process S of Borbély (Hum. Neurobiol. 1: 195-204, 1982.) and contributes to the stability of circadian period. Two predictions follow: diurnal mammals obey Aschoff's rule less consistently during a self-selected light-dark cycle than in constant light, and if light level is increased enough during sleep in diurnal mammals to compensate for eye closure, then Aschoff's rule will hold more consistently. The results are compared with those of Enright's model.

Animals↗
PubMed1984

Some normal and abnormal behavioral syndromes due to transmitter gating of opponent processes.

Opponent processes have long been known to be a basic building block of neural circuits. This article describes properties of opponent processes in which phasic cues and tonic arousal are gated by slowly accumulating chemical transmitters. These opponent processes are called gated dipoles. Gated dipole circuits exhibit syndromes of formal properties that can be used to support or dis-confirm their generative role in a complex body of behavioral data. A wide variety of normal and abnormal behavioral and physiological data exhibit properties analogous to those of gated dipole circuits. These include data about intracellular adaptation, habituation, and rebound; dishabituation and attentional reset by an unexpected event; inverted U properties due to underarousal or overarousal; juvenile hyperactivity; parkinsonism; hyperphagic eating; simple schizophrenia; actions of analgesic agents such as endorphins, electrical brain stimulation, and loud noise; tolerance-withdrawal symptoms, and a new approach to their prevention; normal and abnormal circadian rhythms, as in narcolepsy and manic-depressive psychosis; processing of reinforcing, drive, and motivating signals. Some data predictions derived from gated dipole circuits are also summarized.

Adult↗
PubMed1983

Adaptation and gain normalization: a comment on Ullman & Schechtman (1982).

A well-known process for adaptation and gain normalization is compared with the process described by S. Ullman and G. Schechtman (Proc. R. Soc. Lond. B 216, 299-313 (1982)). A neural interpretation of this process in terms of transmitter gating, slow accumulation, and release is described. Applications to a wide variety of problems in perception, cognition, and motivated behaviour can be made by embedding the gating process into opponent processes, notably shunting on-centre off-surround networks, to form a network module called a gated dipole field.

Adaptation, Physiological↗
PubMed1980

Biological competition: Decision rules, pattern formation, and oscillations.

Competition solves a universal problem about pattern processing by cellular systems. Competition allows cells to automatically retune their sensitivity to avoid noise and saturation effects. All competitive systems induce decision schemes that permit them to be classified. Systems are identified that achieve global pattern formation, or decision-making, no matter how their parameters are chosen. Oscillations can occur due to contradictions in a system's decision scheme. The pattern formation and oscillation results are extreme examples of a complementarity principle that seems to hold for competitive systems. Nonlinear competitive systems can sometimes appear, to a macroscopic observer, to have linear and cooperative properties, although the two types of systems are not equivalent. This observation is relevant to theories about the evolutionary transition from competitive to cooperative behavior.

Journal Article↗
PubMed1977

Pattern formation by the global limits of a nonlinear competitive interaction in n dimensions.

This paper describes a class of nonlinear systems that include processes of pattern formation, short term memory, interpopulation competition, and parallel processing. These systems show how continuously fluctuating data patterns can be processed by noisy populations having finitely many excitable sites. Particular examples are found in vertebrate retina and sensory cortex, as well as certain nonneural developing tissues. After an initial period of seemingly random behavior, that is described by a finite series of iterated decisions or enhancement steps, a global consensus or asymptotic pattern is reached. This is true given any number of competing populations, any mean competition function, and any number of random factors determining interpopulation signals. Which pattern will be chosen can depend on initial data and system structure in a complicated fashion. The results demonstrate a robust design that joins together the dynamics of mass action, the geometry of interpopulation competition, and the statistics of signal generation.

Decision Making↗
PubMed1977

Bisensory stimulation: inferring decision-related processes from P300 component.

Three experiments were conducted to evaluate the P300 component of the human evoked response as an index of bisensory information processing. On different blocks of trials, subjects were presented with auditory stimuli alone, visual stimuli alone, or with audiovisual compounds. In each series there were two possible stimuli, one of which was presented less frequently than the other; the subjects' task was to count the infrequent stimuli. In the first two experiments the information in the two modalities was redundant, whereas in the third the modalities provided nonredundant information. With redundant information, the P300 latency indicated bisensory facilitation when the unimodal P300 latencies were similar; when the unimodal latencies were dissimilar, the bisensory P300 occurred at the latency of the earlier unimodal P300. Reaction times paralleled P300 latency. When the information in the two modalities was nonredundant, both P300 amplitude and reaction-time data indicated interference between the two modalities, regardless of which modality was task relevant. P300 latency and reaction time did not covary in this situation. These data suggest that P300 latency and amplitude do reflect bisensory interactions and that the P300 promises to be a valuable tool for assessing brain processes during complex decision making.

Acoustic Stimulation↗