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At least 505 records · Page 28Linked to original sources
PubMed2006

Role of the olivo-cerebellar system in timing.

Timing has been proposed as a basic function of the cerebellar cortex (particularly the climbing fiber afferents and their sole source, the inferior olive) that explains the contribution of the cerebellum to both motor control and nonmotor cognitive functions. However, whether the olivo-cerebellar system mediates time perception without motor behavior remains controversial. We used event-related functional magnetic resonance imaging to dissociate the neural correlates of the perceptual from the motor aspects of timing. The results show activation of multiple areas within the cerebellar cortex during both perception and motor performance of temporal sequences. The results further show that the inferior olive was activated only when subjects perceived the temporal sequences without motor activity. This finding is most consistent with electrophysiological studies showing decreased responsiveness of the inferior olivary neurons to sensory input during expected, self-produced movement. Our results suggest that the primary role of the inferior olive and the climbing fiber system in timing is the encoding of temporal information independent of motor behavior.

Adult↗
PubMed1995

Attenuating effect of bifemelane on an impairment of mealtime-associated activity rhythm in aged and MK-801-treated rats.

In the present experiment, we examined the attenuating effect of bifemelane hydrochloride (BF), 4-(o-benzyl phenoxy)-N-methylbutylamine hydrochloride, on the impairment of time perception caused by daily scheduled feeding using aged and MK-801-treated rats. When feeding was restricted to a single meal at a fixed time of day (1300-1700 h) for six successive days, young rats exhibited intense locomotor activity 1-3 h before feeding time. Intense locomotor activity was observed for 1200-1700 h even on the fasting day (day 7; mealtime-associated activity). Mealtime-associated activity was impaired in 24-mo-old rats and also in N-methyl-D-aspartate receptor antagonist, MK-801-treated rats. Daily injections of bifemelane at 1700 h for six successive days significantly attenuated the impairment of mealtime-associated activity on the seventh day in a dose-dependent manner in aged rats. In addition, cotreatment of MK-801 with bifemelane blocked the MK-801-induced impairment of mealtime-associated activity. The present study suggests that bifemelane has an enhancing effect on learning and memory performance, such as spatial and temporal perception.

Aging↗
PubMed1978

Binocular utilization of monocular cues that are undetectable monocularly.

The latency time of tracking dynamic random-dot stereograms can be shortened by as much as 100 ms when monocular cues are added by introducing a difference in dot density between target and surround. It has been tacitly assumed that perception time will be reduced only if the added monocular cues are above the detection threshold for each eye. However, the experiments reported here clearly show that stereoscopic performance as measured by an eye tracking task can be greatly enhanced by added monocular cues that cannot be detected. Observers were instructed to track a suddenly displaced vertical bar (portrayed as a dynamic random-dot stereogram) while their eye movements were recorded by EOG. The bar had either a given binocular disparity or zero binocular disparity with respect to its surround. For the target with a disparity (in a wide range), the latency time of tracking decreased by more than 30 ms (10%) as density difference increased from 0 to 4%, whereas in the control conditions with no stereoscopic cues (zero disparity) subjects were unable to track the bar at all within that range of density difference. Thus stereopsis is greatly aided by minimal monocular cues that by themselves elude monocular detection.

Cues↗
PubMed1989

The functions of a nurse: perceptions held by university students of nursing.

The transfer of basic nursing education from the hospital to the tertiary education sector provided unique opportunities for research. This study examined student perceptions of the functions in which they believed nurses were involved in the performance of their role. The entry perceptions of students over three years were examined, during which time perceptions of nursing functions did vary. Two student groups were monitored throughout the three years of the nursing program. It was found that perceptions of nursing functions varied according to curriculum content and exposure to a variety of health and illness experiences as well as role models.

Attitude of Health Personnel↗
PubMed1990

Alternative representations of time, number, and rate.

Three facts of time perception are described based upon a temporal generalization task for rats (the peak procedure) in which food reinforcement is delivered on half the trials following the first lever-press response after some fixed interval after signal onset. (1) The mean response rate as a function of time is a smooth, slightly asymmetric, function with a maximum near the time of reinforcement; (2) the response rate on individual trials is characterized by an abrupt change from a state of low responding to a state of high responding and finally another state of low responding (break-run-break pattern); and (3) the mean response rate in 12-s and 20-s peak procedures is similar when plotted against time relative to the time of reinforcement (superposition). An information-processing version of scalar timing theory is described and compared to an alternative connectionist version of scalar timing theory that involves multiple oscillators and an autoassociation network. Psychological, mathematical and biological descriptions of the two versions are described and some possible extensions of the connectionist version are proposed to deal with perception of number, rate, and spatial orientation.

Animals↗
PubMed1982

Retinal location and visual localization during pursuit eye movement.

Experiments were performed to measure the mislocation of a brief visual stimulus presented during pursuit eye movements in different places over the retina. The results obtained show that the mislocation for regions 5 degrees from fovea in the direction of motion is greater than in fovea. This fact shows that some kind of reorganization takes place in the visual localization mechanisms during pursuit eye movements. The results cast doubts on the concept of "perception time" which is often used to explain the visual mislocation phenomenon.

Adult↗
PubMed2006

Time, from psychology to neurophysiology: a historical view.

Two aspects of psychology and physiology of time are dealt with in this paper: the way time perception was increasingly studied during the 19th century by scientists, including many physicists, and the way the temporal properties of the nervous system were discovered and explored by physiologists. The neurophysiological correlation between both aspects still remains to be explained. The relationship between time consciousness and consciousness mechanisms was often guessed by philosophers and looked for by scientists. It remains a major subject of investigation in neuroscience as well as a philosophical puzzle.

Animals↗
PubMed1989

Anticholinergic effects on memory: benztropine versus amantadine.

To evaluate anticholinergic effects on cognition and other functions, we studied 60 healthy volunteers in a double-blind crossover trial of two antiparkinsonian agents, benztropine and amantadine. Benztropine 4 mg/day, but not amantadine 200 mg/day, impaired free recall and perception of time, and subjects' perception of their own memory impairment was significantly greater with benztropine. Side effects in general were worse with benztropine, particularly such anticholinergic effects as dry mouth and blurred vision, and benztropine decreased measured salivary flow to a significantly greater degree than amantadine. Our findings support the hypothesis that drugs that decrease cholinergic transmission impair storage of new information into long-term memory, but have little effect on retrieval from memory or on tasks involving only immediate memory. Clinically, anticholinergic agents can levy a considerable burden on memory and time perception.

Adolescent↗
PubMed2006

Hyperbolic discounting may be reduced to electrical coupling in dopaminergic neural circuits.

Loss of self-control in drug addicts (e.g. cocaine and amphetamine dependent patients) has been associated with hyperbolic discounting of delayed rewards (i.e., inconsistency in intertemporal choice). Neurobiophysical mechanisms underlying hyperbolic discounting are still unknown in spite of recent extensive work in neuroeconomics. Understanding of neuronal mechanisms of hyperbolic discounting is important for establishing neuropharmacological treatment of addiction. At the cognitive level, previous studies have indicated that psychophysics of time-estimation (i.e., Weber-Fechner law and Steven's power law of time-perception) may explain inconsistency in intertemporal choice. Regarding neuronal substrates of time-estimation, drugs of abuse dramatically change time-estimation, indicating that dopaminergic activities may mediate time-estimation. With respect to neuronal changes induced by drugs of abuse, recent studies have revealed that gap junction proteins (e.g., connexin 36) in dopamine neurons are increased by an self-administration of dopaminergic drugs such as cocaine and amphetamine. However, it has been yet to be examined how the enhanced electrical coupling due to substance administration induces addiction. Furthermore, a recent biophysical modelling study has demonstrated that the effect of the psychophysical laws are potentiated by non-synaptic electrical coupling between neurons via gap junctions. Based on these current findings, we hypothesized that hyperbolic discounting may be reduced to biophysical characteristics of dopamine neural circuits, that is, electrical coupling between time-encoding dopaminergic neurons via gap junctions. The present hypothesis states that drugs of abuse may induce addiction by exacerbating subject's impulsivity (a discount rate) and inconsistency (hyperbolicity) in intertemporal choice partly due to enhanced expression of gap junction proteins in dopaminergic neurons. Possible psychopharmacological treatments of impulsivity in drug addicts implied by our present hypothesis, e.g., administration of a gap junction blocker, are discussed.

Brain↗
PubMed1983

Hemisphere specialization of the animal brain for information processing principles.

The experiments were performed on white rats. Different techniques for forming conditioned reflexes were used. Hemisphere cortex inactivation was carried out by means of spreading depression. The right hemisphere was shown to dominate for space perception, simultaneous information processing, concrete characteristics perception, and deductive processing; the left hemisphere was shown to dominate for time perception, successive information processing, abstract characteristics perception, and inductive processing. A hypothesis of induction and deduction being the main factors determining function lateralization in the hemispheres of the animal brain was put forward.

Animals↗
PubMed1996

Tasks and timing in the perception of linguistic anomaly.

Three experiments were conducted to investigate the relative timing of syntactic and pragmatic anomaly detection during sentence processing. Experiment 1 was an eye movement study. Experiment 2 employed a dual-task paradigm with compressed speech input, to put the processing routines under time pressure. Experiment 3 used compressed speech input in an anomaly monitoring task. The outcomes of these experiments suggest that there is little or no delay in pragmatic processing relative to syntactic processing in the comprehension of unambiguous sentences. This narrows the possible explanations for any delays that are observed in the use of pragmatic information for ambiguity resolution.

Cognition↗
PubMedDate not supplied

Attention deficit/hyperactivity disorder: characteristics, interventions and models.

An epidemiological study of Attention Deficit/Hyperactivity Disorder (ADHD) suggests that the prevalence may be two to three times higher than the figure of 3-5% often cited. In addition, the data suggest that both underdiagnosis and overdiagnosis occur frequently. Rodent animal models of ADHD, like the Spontaneously Hypertensive Rat (SHR) and other rat models such as those with chemical and radiation-induced brain lesions and cerebellar stunting, and the Coloboma mouse model exhibit clear similarities with several aspects of the human disorder and should prove useful in studying specific traits. Operant behavioral tasks that model learning, short-term memory and simple discriminations are sensitive to ADHD and methylphenidate has been shown to normalize ADHD performance in a short-term memory task. Recent findings challenge not only the current postulate that response inhibition is a unique deficit in ADHD, but also the concepts of ADHD and its treatment, which presume intact perceptual abilities. Time perception deficits may account, in part, for the excessive variability in motor response times on speeded reaction time tasks, motor control problems and motor clumsiness associated with ADHD. The Multimodality Treatment Study of ADHD (MTA) provided data suggesting that pharmacological interventions that included systematic and frequent follow-up with parents and teachers, with or without psychosocial interventions, are superior to psychosocial interventions or standard community care alone. Additionally, the MTA was one of the first studies to demonstrate benefits of multimodal and pharmacological interventions lasting longer than 1 year. Imaging studies have demonstrated differences in brain areas in children with ADHD: anterior corpus callosum, right anterior white matter, and cerebellar volumes are all decreased in children with ADHD and there is less brain asymmetry in ADHD subjects. Additionally, functional imaging studies, coupled with pharmacological manipulations, suggest decreased blood flow and energy utilization in prefrontal cortex and striatum and the dysregulation of catecholamine systems in persons with ADHD.

Animals↗
PubMed2006

Spatially localized distortions of event time.

A fundamental question about the perception of time is whether the neural mechanisms underlying temporal judgements are universal and centralized in the brain or modality specific and distributed. Time perception has traditionally been thought to be entirely dissociated from spatial vision. Here we show that the apparent duration of a dynamic stimulus can be manipulated in a local region of visual space by adapting to oscillatory motion or flicker. This implicates spatially localized temporal mechanisms in duration perception. We do not see concomitant changes in the time of onset or offset of the test patterns, demonstrating a direct local effect on duration perception rather than an indirect effect on the time course of neural processing. The effects of adaptation on duration perception can also be dissociated from motion or flicker perception per se. Although 20 Hz adaptation reduces both the apparent temporal frequency and duration of a 10 Hz test stimulus, 5 Hz adaptation increases apparent temporal frequency but has little effect on duration perception. We conclude that there is a peripheral, spatially localized, essentially visual component involved in sensing the duration of visual events.

Adaptation, Physiological↗
PubMed1988

The effect of focal interictal spikes on perception and reaction time. I. General considerations.

The effect of focal interictal spikes on visual perception and reaction time (RT) was studied in 3 subjects, by means of a computerized system of spike detection, presentation of visual stimuli, and timing of a button press. A total of 8646 such trials were analyzed, comparing spike-locked and control performances within the same subject. For stimuli locked to spikes involving visual cortex, both the rate of non-responses (non-perceptions) and the RTs of responses were increased (P less than 0.0001) in all 3 subjects. The magnitude of this effect was roughly proportional to the amplitude and breadth of field of the spike. Focal spikes in cortical areas uninvolved in the visual motor task did not impair performance. These findings indicate that single focal interictal spikes transiently disrupt aspects of cortical functioning, at least in the few subjects studied so far. This may have developmental and therapeutic implications for patients with very frequent interictal spikes, even thought they may not have seizures or their seizures may be well controlled.

Action Potentials↗
PubMed1981

Relationship between figure-ground perception and viewing time in a ball-catching task.

This investigation determined the relationship between figure-ground perception and viewing time in a ball-catching task of 34 beginning, 34 intermediate, and 30 advanced tennis players. Also analyzed were the differences between the sexes and levels of tennis skill on figure-ground perception, on the ball-catching task, and viewing time. Findings indicated that there is no relationship between figure-ground perception and viewing time. No differences were noted between the sexes or levels of tennis skill on figure-ground perception; however, there were significant differences in success in ball-catching and viewing times.

Adult↗
PubMed2004

Therapeutic touch, quiet time, and dialogue: perceptions of women with breast cancer.

PURPOSE/OBJECTIVES: To compare the perceptions of women with breast cancer to an experimental therapeutic touch (TT) plus dialogue nursing intervention with perceptions of a control quiet time plus dialogue nursing intervention. DESIGN: Qualitative study based on the Science of Unitary Human Beings. SETTING: Data collected as part of a larger experimental study of the effects of TT on pre- and postoperative anxiety and mood and postoperative pain in women with breast cancer. SAMPLE: 18 women with early-stage breast cancer. METHODS: Telephone interviews at the completion of an experimental or control nursing intervention administered in the women's homes before and after breast cancer surgery. MAIN RESEARCH VARIABLES: Women's perceptions of participation in a study of the effects of dialogue and TT or quiet time. FINDINGS: Content analysis of transcribed telephone interviews revealed few differences in participants' perceptions of experimental and control interventions. Only participants who received the experimental intervention reported body sensations, and only participants in the control group inquired about the study and its purpose. Regardless of experimental or control intervention participation, women expressed feelings of calmness, relaxation, security, and comfort and a sense of awareness. The few women who commented about the nurse who administered the experimental or control intervention indicated that the nurse was empathetic, concerned, supportive, or helpful. CONCLUSIONS: The women regarded either nursing intervention as a positive experience. Some also expressed positive regard for the research nurse. IMPLICATIONS FOR NURSING: Nurses who are not trained in the administration of TT may use quiet time and dialogue to enhance feelings of calmness and relaxation in patients with breast cancer.

Anxiety↗