Postsynaptic mechanism of habituation of turtle cortical neurons to moving stimuli

An investigation was made into the change in the amplitude of evoked potentials and intracellular slow potentials of the turtle general cortex units in response to a periodic movement of a monotonous stimulus, a black band, across the visual field. The recorded depression of responses possesses all the properties of habituation. The first presentations of the monotonous stimulus produce a generalized habituation, gradually replaced by a selective habituation to the monotonous stimulus, as the number of stimulations increases. It has been shown that it is possible to disinhibit the amplitudes of the evoked potentials and intracellular slow potentials of cortical neurones to moving black bands which form part of the monotonous stimulus. A conclusion has been drawn that habituation of the turtle cortical units to moving stimuli is due to a postsynaptic mechanism.     

Habituation of the EEG arousal response in rats: Short- and long-term effects, frequency specificity, and wake–sleep transfer.

In 3 experiments with 78 male Holtzman albino rats, presentation of auditory stimuli over interstimulus intervals (ISIs) of several minutes to sleeping Ss produced significant habituation of the EEG arousal response. The arousal response habituated to an asymptote after only 2 or 3 stimulus presentations. Little or no spontaneous recovery occurred between sessions separated by 24 or 72 hrs. The habituation produced by a single stimulus presentation was retained for at least 24 hrs, and orderly habituation was shown with a 24-hr ISI. Approximately 90% retention of habituation was shown 32 days following 10 stimulus presentations, and some degree of retention was shown for as long as 50 days. After habituation had reached a long-term asymptote, 600 stimulus presentations over 2-sec ISIs produced further response decrements, but these decrements recovered completely within a matter of minutes and responsiveness returned to the previously established long-term asymptote. Habituation was shown to be frequency-specific over both 24-hr and 32-day intervals. Habituation produced by stimulus presentations to awake Ss transferred to the condition in which stimuli were presented to sleeping Ss. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Habituation of prepulse inhibition of the startle reflex using an auditory prepulse close to background noise.

This study examined whether prepulse inhibition habituates with repeated presentation of the prepulse alone. Prepulse inhibition was determined by measuring the decrement in the startle response when the acoustic startle-eliciting stimulus was preceded by an auditory prepulse. Rats received repetitive exposures of the same auditory prepulse alone (experimental condition) and of a visual prepulse alone (control condition). To reduce habituation of startle itself and the possible dishabituating influence the startle stimulus might have on habituation of prepulse inhibition, startle stimulus presentations were infrequently interspersed among a much larger number of prepulse-alone presentations. Stimulus-specific habituation of prepulse inhibition occurred using an auditory prepulse 2.5 dB, but not 13 dB, above background noise. Implications are discussed for the role of prepulse inhibition in sensory gating. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does oral experience terminate ingestion?

Using data from studies of ingestive behavior in developing rat pups we demonstrate how oral experience can contribute to the termination of ingestion. In rat pups, repeated oral stimulation with sweet solutions causes a decline in oral responsiveness. The diminished responsiveness is specific to the flavor of the stimulus experienced orally and can persist for several hours. We suggest that this experience-based decrement in responsiveness is best considered "oral habituation" and that oral habituation largely accounts for the onset of satiety. Post-ingestive feedback signals may have their influence through the oral habituation process or act in the context of oral habituation. Oral habituation is also shown to depend on the pattern of stimulus presentation, a phenomenon that adds considerable complexity to assessing the contributions of oral experience to satiety. The concept of oral habituation may be useful in understanding the immediate control of ingestion and the moment-to-moment expression of ingestive behavior in adult animals.     

Repetitive exposure does not attenuate the sensory impact of the habituated stimulus.

Examined the hypothesis that habituation may reduce the perceived intensity of the repeated stimulus, using 12 naive male albino Holtzman rats. A brief electric shock that elicited a reflexive jump and inhibited a noise-induced startle reaction was tested for its eliciting and inhibiting potentials following a series of shock presentations in a habituation session. Repeated presentations of the shock stimulus diminished the elicited reaction but did not reduce its inhibitory effect on the acoustic startle reaction. This finding reveals that habituation does not affect functional stimulus intensity. It was also found that habituation training with the shock enhanced the reaction to a control acoustic stimulus, an indication of the nonspecific nature of sensitization. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of mesencephalic reticular formation lesions on habituation of startle and lick suppression responses in the rat.

In 2 experiments with 43 male albino Holtzman rats, extensive damage to the mesencephalic reticular formation (MRF) altered long-term habituation of the acoustic startle response without disrupting short-term habituation. Ss with MRF lesions, although initially neither more nor less responsive than controls, could not attain as low a long-term asymptote of habituation as could control Ss with repeated presentations of an auditory stimulus. Changing the quality of the auditory stimulus abolished the asymptotic difference in responsiveness. With repeated presentations of the 2nd auditory stimulus, control Ss again reached a significantly lower long-term habituation asymptote than did Ss with MRF lesions. The course of long-term habituation for the 2 groups suggested a disruption of an extrinsic, inhibitory habituation process by the lesions. The effects of MRF lesions were specific to the acoustic startle response. Control Ss and those with lesions showed comparable response levels, short-term habituation, and long-term habituation of the lick suppression response. Responsiveness and habituation to tactile stimuli were comparable for the 2 groups on both lick suppression and startle response measures. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of habituation training on compound conditioning are not reversed by an associative activation treatment.

Rats received habituation to either 2 compound flavors (AX and BY; the activation group) or a compound and an element alone (AX and Y; the habituation group). They also received additional presentations of Y alone either after (Experiment 1) or intermixed (Experiment 2) with habituation. In the habituation group, A had undergone habituation whereas B had not; in the activation group, both A and B had undergone habituation, but presenting Y alone should result in associative activation of B and that, according to G. Hall (2003), should increase B's efficacy. A supplementary experiment demonstrated that the presentation of Y does activate a representation of B. In both experiments, an aversion was established to AB, and subsequently the habituation group showed a greater aversion to B than to A. However, in neither experiment was there any indication that the activation group showed a greater aversion to B than to A. These results are inconsistent with the suggestion that the associative activation of a stimulus representation in the absence of the stimulus reverses the effects of habituation training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Habituation of fright and arousal responses in the teleosts Carassius auratus and Rutilus rutilus..

Examined the habituation of fright and arousal responses of the goldfish and roach to the repeated operation of a plunger in the water. The early response was fright, which habituated, and then the response characteristic of arousal appeared, which habituated as well. Longer intervals between stimuli required more presentations of the stimulus for habituation to occur in goldfish. Roaches required more presentations of the stimulus than goldfish for the responses to habituate, and telencephalic ablation severely impaired habituation of arousal, though not fright responses. Results are discussed in relation to recent work on arousal, habituation, and telencephalic function in fish. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning the unconditioned response: Modification of the rabbit's (Oryctolagus cuniculus) unconditioned nictitating membrane response.

Conditioning-specific reflex modification (CRM) occurs when classical conditioning modifies responding to a unconditioned stimulus/stimuli (UCS) in the absence of a conditioned stimulus (CS). Three experiments monitored rabbit (Oryctolagus cuniculus) nictitating membrane unconditioned responses to 5 intensities and 4 durations of periorbital electrical stimulation before and after CS or UCS manipulation. CRM occurred after 12 days of CS-UCS pairings but not following unpaired CS/UCS presentations or restraint. CRM survived CS-alone and CS/UCS-unpaired extinction of the conditioned response (CR) but not presentations of the UCS alone, although CRs remained intact. Thus, CRs could be weakened without eliminating CRM and CRM could be weakened without eliminating CRs. Data indicate CRM is a reliable, associative effect that is more than a generalized CR and may not be explained by habituation, stimulus generalization, contextual conditioning, or bidirectional conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deficits in habituation of cardiac arousal responses incurred by telencephalic ablation in goldfish, Carassius auratus, and their relation to other telencephalic functions

The effects of telencephalic ablation on the habituation of cardiac arousal responses in goldfish was studied. The ablation was performed either by ligating the telencephalon of habituated fish between stimulus presentations or by aspiration prior to habituation. The former technique caused dishabituation; the latter, a slower rate of habituation than that of sham-operated controls. The habituation deficit incurred by surgical ablation was found to decline with time, being small after 2 wk. The results are discussed in relation to other telencephalic involvements in behavior and to the plasticity of other parts of the brain which enables them to assume telencephalic functions.     

Habituation and tonic immobility in domestic chickens

The habituation of tonic immobility in chickens was examined in six studies. It was shown that repeated elicitation of immobility, and not just handling, was responsible for reduced response durations after multiple exposures to manual restraint. Habituation was a function of the number of stimulus presentations and, in addition, proved surprisingly durable, with diminished reactions using lasting at least 2.5 mo. Strain differences were found in the number of trials required to reach a criteria of habituation, and habituation proceeded faster when immobility termination was self-paced as opposed to experimenter induced. Also, massed trials produced robust sensitization effects rather than diminished responsiveness.     

"Novelty" neurons in the frog auditory system

Some neurones in the torus semicircularis of paralyzed lake frogs (Rana ridibunda) exhibited strong response habituation to tonal bursts following with interstimuli intervals of 1 to 5 sec. The habituation became less evident with a devrease of the repetition rate or increase of the stimulus intensity. These units revealed the phenomenon of "postzero" habituation. The frequency selectivity of the units exhibited by their responses to the first stimulus presentation was very poor. Usually the habituation occurred within a wide frequency band, although there were some exceptions. Afther the habituation was completed, the unit's response could be elicited by tones of a different frequency. The more distant on the frequency scale the tones were, the more vigorous was the reaction. Some properties of these "novelty" units can be explained by assuming that they are multipolar neurones located in the nucleus magnocellularis of the torus.     

Neonatal habituation and dishabituation to tactile stimulation during sleep.

Two experiments examined habituation and dishabituation of behavioral responding to repeated presentations of a tactile stimulus (brush stroke) in 48 newborns during the 1st epoch of active-quiet sleep following a feeding. Exp I demonstrated habituation to a repeatedly presented brush stroke to the ear but failed to demonstrate dishabituation (i.e., response recovery) to the original brush stroke following an intense auditory stimulus (86 dB rattle sound). A post hoc control group showed that the intense auditory stimulus had suppressed subsequent responding to the tactile stimulus. Exp II replicated the habituation phase of Exp I and demonstrated response recovery to stimulation at a novel tactile site and to an auditory probe. Results indicate that the habituation paradigm used in infancy research could be successfully extended to the tactile modality. It is also suggested that prior auditory stimulation, but not prior tactile stimulation, might direct attention away from a subsequently presented tactile stimulus. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Habituation in goldfish (Carassius auratus) is impaired by increased interstimulus interval, interval variability, and telencephalic ablation.

Goldfish (Carassius auratus) were fitted with electrodes and buccal catheters for monitoring EKGs and ventilations, respectively. A 2-s "light-on" stimulus was repeatedly presented to groups of fish at fixed interstimulus intervals (ISIs) of 1 or 2 min or at variable ISIs with a mean duration of 1 or 2 min. Normal fish, fish with telencephalic ablation, and fish with sham operations were compared for responsiveness and habituation to repeatedly presented stimuli. The longer the ISI, the greater the number of stimuli that were required for habituation. Increased ISI variability also decreased the rate of habituation. Furthermore, fish with telencephalic ablation had significantly slower habituation rates with both fixed and variable ISI schedules. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Forgetting rates in neuropsychiatric disorders

OBJECTIVE: Previous studies have attributed accelerated forgetting rates on recognition memory tasks to temporal lobe pathology, but findings in some patient groups may have been attributable to metabolic disruption. Findings in psychiatric disorders such as schizophrenia are conflicting. The purpose of the present study was to compare forgetting rates in patients with confusional states (post-electroconvulsive therapy (post-ECT), delirium), with those obtained in schizophrenic patients (with putative temporal lobe pathology), non-ECT depressed patients, and healthy controls. The findings could also be compared with previous reports in patients with head injury, focal structural lesions, and Alzheimer's dementia. METHODS: Two studies employed a picture recognition task to examine forgetting rates, the first between delays of 1 minute, 15 minutes, and 30 minutes, and the second between delays of 10 minutes, 2 hours, and 24 hours. RESULTS: There were no significant differences in forgetting rates between 1 minute and 30 minutes, but the ECT group showed accelerated forgetting between 10 minutes and 2 hours compared with healthy controls, associated with a rapid decline in "hit rate". This was not attributable to differential changes in either depression or severity of memory impairment. There were no differences in forgetting rates across the other subject groups. CONCLUSION: Post-ECT confusional state patients (similarly to "within post-traumatic amnesia" patients with head injury) show accelerated forgetting on a recognition memory task and, in this, they contrast with patients who have focal structural lesions or widespread cortical atrophy. Accelerated forgetting may reflect the effect of disrupted cerebral metabolism on either "consolidation" or memory "binding" processes.     

Comparative potency of tactile, auditory, and visual stimulus repetition in eliciting activated forebrain EEG in the rabbit.

Examined whether certain modalities of stimulation are more effective than others in eliciting immobility-related, atropine-sensitive neocortical low-voltage fast activity and hippocampal rhythmical slow activity from the rabbit. Four Dutch belt male rabbits were used in a series of studies in which the number of stimulus presentations; stimulus modality; interstimulus interval; or drug treatment—saline, atropine sulfate (60 mg/kg, ip), and low-dose pentobarbital—were varied. More pronounced activation and less pronounced habituation followed tactile than auditory and visual stimulation. It is suggested that atropine-sensitive EEG activity may be importantly involved in the central programming, initiation, and guidance of movement. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of auditory P300 habituation from active and passive conditions

The P3(00) event-related brain potential (ERP) was elicited using auditory stimuli and tasks in which the subject discriminated between standard and target tones or with passive task conditions in which the subject did not respond to either the standard or target stimuli. All stimulus presentations consisted of a series of ten-tone sequences in which the first six tones were always the standard and one of the last four tones was the target. The passive tasks were presented twice to assess for habituation effects. P3 amplitude was largest for the oddball task compared to the passive tasks, and repetition of the passive paradigm demonstrated a decrease in amplitude between conditions. P3 amplitude did not decrease across trials within any of the separate response conditions. P3 latency was shorter for the active discrimination relative to the passive tasks. The results suggest that the P3 component can be obtained reliably with passive procedures and does not habituate within a trial block. However, repeated blocks of passive stimulus presentations will cause the P3 ERP to diminish in size.     

Intentional forgetting is easier after two "shots" than one.

Three experiments evaluated whether the magnitude of the list-method directed forgetting effect is strength dependent. Throughout these studies, items were strengthened via operations thought to increase context strength (spaced presentations) or manipulations thought to increment the item strength without affecting the context strength (processing time and processing depth). The assumptions regarding which operations enhance item and context strength were based on the "one-shot" hypothesis of context storage (K. J. Malmberg & R. M. Shiffrin, 2005). The results revealed greater directed forgetting of strong items compared with weak items, but only when strength was varied via spaced presentations (Experiment 3). Equivalent directed forgetting was observed for strong and weak items when strengthening operations increased item strength without affecting the context strength (Experiments 1 and 2). These results supported the context hypothesis of directed forgetting (L. Sahakyan & C. M. Kelley, 2002). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rate of forgetting in dementia and depression.

Patients with mild dementia of the Alzheimer's type (DAT), patients with major depression, and normal control subjects were examined for rate of forgetting line drawings of common objects after the groups had been equated for acquisition by the variation of stimulus exposure time. Depressed and DAT patients demonstrated learning impairments, but only the DAT group showed rapid forgetting in the first 10 min after learning to criterion. This finding suggests that some form of deficient consolidation contributes to memory loss in DAT but not in depression and implicates the disruption of different psychobiological mechanisms in these disorders. The rate of forgetting paradigm may be clinically useful for distinguishing patients with early DAT from elderly depressed patients with memory deficits. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The decerebrate human: associative learning

Phasic changes in cardiac reactivity to innocuous stimuli, presented in a sensory disparity paradigm, were used to evaluate habituation and learning processes in five decerebrate subjects. Three subjects showed systematic changes over trials in the pattern of cardiac response to simple auditory or visual stimuli, indicative of habituation. In addition, tests for associative learning were given after repeated presentations of two paired stimuli. The appearance of a marked cardiac orienting response, to the unpredictable omission of the second stimulus, documented the development of a conditioned association in these same three subjects. One additional subject failed to show a consistent pattern of response to the stimuli, and another demonstrated a consistent response which was not subject to habituation. Overall, these findings support the view that learning processes are not solely the product of the cerebral hemispheres, but reflect general integrative features of the human neuraxis.