Antisickness conditioning using a nausea-producing nondrug cue.

Most drugs induce conditioned taste aversions and are therefore commonly supposed to produce nausea and sickness. Paradoxically, some drugs appear to lose induction capability when made to serve as a cue for a 2nd drug that produces more severe sickness, perhaps through selective association with a hypothetical homeostatic or antisickness aftereffect of sickness. Using drug–drug pairings has made antisickness conditioning theory difficult to validate. Rotation serves in lieu of a drug cue in rats. Rotation–drug pairings eliminate drug interactions and enable the sorts of parametric manipulations required to validate the theory. By postulating a common sickness mechanism to explain both taste aversion and aversion failure, the theory places the phenomenon within an adaptive evolutionary framework. Successful application could yield a direct countermeasure to severe nausea in clinical settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual processing of multidimensional and unidimensional auditory stimuli.

Stimulus context (the distribution of stimulus values) can strongly affect both perception and judgment. In 14 experiments, the method of magnitude estimation revealed 2 fundamentally different kinds of context effect in loudness. An assimilative effect dominated when stimuli varied unidimensionally (in intensity only). But a contrastive, or adaptationlike, effect dominated when stimuli varied multidimensionally (in frequency and intensity). In Exp 15, direct loudness comparison revealed a potent, adaptational process specific to the signal frequency. Taken together, these and other results are compatible with the view that loudness perception and judgment reflect the net outcome of 2 different contextual processes: a relatively early (though probably not peripheral) process of perceptual adaptation and a later process of response-dependent assimilation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Processing auditory information: Interference from an irrelevant cue.

In a choice RT task, 64 undergraduates pressed either a right- or left-hand key in response to directional commands provided by 400- and 1000-cps tones. On monaural trials, RT was significantly faster when the meaning of the tonal command corresponded with the ear in which it was heard (corresponding trials) than when it did not (noncorresponding trials). A comparison of monaural with binaural RT indicated that this Tonal Command * Ear Stimulated interaction was due to interference on the noncorresponding monaural trials rather than facilitation on the corresponding trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibitory influences on asynchrony as a cue for auditory segregation.

A harmonic that begins before the other harmonics contributes less than they do to vowel quality. This reduction can be partly reversed by accompanying the leading portion with a captor tone. This effect is usually interpreted as reflecting perceptual grouping of the captor with the leading portion. Instead, it has recently been proposed that the captor effect depends on broadband inhibition within the central auditory system. A test of psychophysical predictions based on this proposal showed that captor efficacy is (a) maintained for noise-band captors, (b) absent when a captor accompanies a harmonic that continues after the vowel, and (c) maintained for 80 ms or more over a gap between captor offset and vowel onset. These findings support and refine the inhibitory account. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trial development of unit response changes during conditioning in cats.

Recorded single-cell and evoked potential (EP) activity in the postcruciate cortex of 45 acutely prepared cats during a classical conditioning procedure. The temporal pattern of response (PSH) of the neuron was separated into 3 components, and the trial development of learning changes for these components was examined individually. Changes over trials in the similarity of the EP waveform and the unit PSH were also examined. The unit response components showed changes in response at different trial periods; these changes could not be accounted for by changes at lower brain levels that projected to the cortex. This suggests that local learning changes were taking place in the cortex. The EP-PSH similarity decreased for neurons showing the largest changes in response during conditioning. Since the EP reflects the response of the whole population of neurons and a majority did not show learning changes, this could account for the observed decrease. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Choice and contingency in the development of behavioral autonomy during instrumental conditioning.

In two experiments hungry rats received extensive training to lever press for food outcomes before one outcome was devalued by aversion conditioning and responding tested in extinction. If the rats were trained on a concurrent schedule in which two responses yielded different outcomes, performance during the extinction test was reduced by devaluation of the associated outcome. By contrast, if a single response was trained concurrently with the noncontingent presentations of the other outcome, test performance was insensitive to devaluation of the contingent outcome. This finding demonstrates that training on a schedule that offers a choice between responses that yield different outcomes prevents the onset of behavioral autonomy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual fear conditioning, conjunctive representations, pattern completion, and the hippocampus.

Impaired contextual fear conditioning produced by damage to the hippocampus has been attributed to the loss of a conjunctive representation of the features of the context. There is, however, no direct evidence that conjunctive representations contribute to contextual fear conditioning. These experiments addressed this issue and found support for the conjunctive representation view. Two results made this point: (a) Preexposure to the conditioning context, but not to its separable features, facilitated contextual fear conditioning, and (b) generalization of fear conditioning to similar contexts was enhanced by preexposure to the context used to test for generalization. These results are interpreted as pattern completion to the preexposed context during the conditioning episode. They support the view that a conjunctive representation of context plays an important role in contextual fear conditioning and that the impairments produced by damage to the hippocampus result from the loss of this conjunctive contribution. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial auditory thalamic nuclei are necessary for eyeblink conditioning.

The auditory conditioned stimulus (CS) pathway that is necessary for delay eyeblink conditioning was investigated with induced lesions of the medial auditory thalamus contralateral to the trained eye in rats. Rats were given unilateral lesions of the medial auditory thalamus or a control surgery followed by twenty 100-trial sessions of delay eyeblink conditioning with a tone CS and then five sessions of delay conditioning with a light CS. Rats that had complete lesions of the contralateral medial auditory thalamic nuclei, including the medial division of the medial geniculate, suprageniculate, and posterior intralaminar nucleus, showed a severe deficit in conditioning with the tone CS. Rats with complete lesions also showed no cross-modal facilitation (savings) when switched to the light CS. The medial auditory thalamic nuclei may modulate activity in a short-latency auditory CS pathway or serve as part of a longer latency auditory CS pathway that is necessary for eyeblink conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Timing during inhibitory conditioning.

Analyses of second-by-second conditioned responding into a food receptacle by hungry rats (Rattus norvegicus) found that inhibition varies across the duration of a conditioned stimulus (CS) in a manner consistent with initial training. Variations in the arrival time of the unconditioned stimulus (US) supported temporally specific suppression of responding (Experiment 1). Summation and retardation tests (Experiments 2 and 3, respectively) revealed that points of greatest inhibition coincided with US omission at the time normally specified by the excitor. Our data provide a clear demonstration of fine-grained changes in the time course of inhibitory conditioning for the first time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampectomy disrupts auditory trace fear conditioning and contextual fear conditioning in the rat

The hippocampus is believed to be an important structure for learning tasks that require temporal processing of information. The trace classical conditioning paradigm requires temporal processing because the conditioned stimulus (CS) and the unconditioned stimulus (US) are temporally separated by an empty trace interval. The present study sought to determine whether the hippocampus was necessary for rats to perform a classical trace fear conditioning task in which each of 10 trials consisted of an auditory tone CS (1 5-s duration) followed by an empty 30-s trace interval and then a fear-producing floor-shock US (0.5-s duration). Several weeks prior to training, animals were anesthetized and given aspiration lesions of the neocortex (NEO; n = 6), hippocampus and overlying neocortex (HIPP; n = 7), or no lesions at all (control; n = 6). Approximately 24 h after trace conditioning, NEO and control animals showed a significant decrease in movement to a CS-alone presentation that was indicative of a conditioned fear response. Animals in the HIPP group did not show conditioned fear responses to the CS alone, nor did a pseudoconditioning group (n = 7) that was trained with unpaired CSs and USs. Furthermore, all groups except the HIPP group showed conditioned fear responses to the original context in which they received shock USs. One week later, HIPP, NEO, and control animals received delay fear-conditioning trials with no trace interval separating the CS and US. Six of seven HIPP animals could perform the delay version, but none could perform the trace version. This result suggests that the trace fear task is a reliable and useful model for examining the neural mechanisms of hippocampally dependent learning.     

Reaction time as a function of the cue properties of an auditory display.

An attempt was made to increase the speed of processing verbal directional commands by using the ear stimulated to provide a relevant directional cue. In a choice reaction-time task, Ss pressed the right- or left-hand key in response to: (1) binaural "right" or "left" commands, (2) monaural "right" or "left" commands in the ear corresponding to the content of the command, and (3) monaural pure tones. Responses to the binaural commands were significantly slower than to the other 2 conditions, and responses to the monaural commands were significantly slower than to the monaural tones. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fear conditioning to discontinuous auditory cues requires perirhinal cortical function.

Pretraining lesions of rat perirhinal (PR) cortex impair fear conditioning to ultrasonic vocalizations (USVs) but have no effect on conditioning to continuous tones. This study attempted to deconstruct USVs into simpler stimulus features that cause fear conditioning to be PR-dependent. Rats were conditioned to one of three cues: a multicall 19-kHz USV, a 19-kHz discontinuous tone, and a 19-kHz continuous tone. The discontinuous tone duplicated the on/off pattern of the individual calls in the USV, but it lacked the characteristic frequency modulations. Well-localized neurotoxic PR lesions impaired conditioning to the USV, the discontinuous tone, and the training context. However, PR lesions had no effect on conditioning to the continuous tone. The authors suggest that the lesion effects on fear conditioning to both cues and contexts reflect the essential role of PR in binding stimulus elements together into unitary representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Induction of receptive field plasticity in the auditory cortex of the guinea pig during instrumental avoidance conditioning.

Classical tone conditioning shifts frequency tuning in the auditory cortex to favor processing of the conditioned stimulus (CS) frequency versus other frequencies. This receptive field (RF) plasticity is associative, highly specific, rapidly acquired, and indefinitely retained—all important characteristics of memory. The investigators determined whether RF plasticity also develops during instrumental learning. RFs were obtained before and up to 24 hr after 1 session of successful 1-tone avoidance conditioning in guinea pigs. Long-term RF plasticity developed in all subjects (N?=?6). Two-tone discrimination training also produced RF plasticity, like classical conditioning. Because avoidance responses prevent full elicitation of fear by the CS, long-term RF plasticity does not require the continual evocation of fear, suggesting that neural substrates of fear expression are not essential to RF plasticity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Procedural memory system supports single cue trace eyeblink conditioning in medial temporal lobe amnesia.

A number of studies investigating trace eyeblink conditioning have found impaired, but not eliminated, acquisition of conditioned responses (CRs) in both animals and humans with hippocampal removal or damage. The underlying mechanism of this residual learning is unclear. The present study investigated whether the impaired level of learning is the product of residual hippocampal function or whether it is mediated by another memory system that has been shown to function normally in delay eyeblink conditioning. Performance of bilateral medial temporal lobe amnesic patients who had a prior history of participating in eyeblink conditioning studies was compared to a control group with a similar training history and to an untrained control group in a series of single cue trace conditioning tasks with 500 ms, 250 ms, and 0 ms trace intervals. Overall, patients acquired CRs to a level similar to the untrained controls, but were significantly impaired compared to the trained controls. The pattern of acquisition suggests that amnesic patients may be relying on the expression of previously acquired, likely cerebellar based, procedural memory representations in trace conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual conditioning and the control of copulatory behavior by species-specific sign stimuli in male Japanese quail.

Three experiments were conducted to identify species-specific sign stimuli sufficient to elicit copulatory behavior in male Japanese quail and to determine how learning is involved in the control of behavior by these sign stimuli. In Exp 1, sexually experienced Ss were tested for copulatory behavior with a live female quail and with a model consisting of a female quail's head and neck mounted in front of a foam pad. Comparable levels of copulatory behavior were observed in the two tests, indicating that static visual cues provided by a female quail's head and neck are sufficient to elicit copulatory behavior in this species. Exp 2 showed that male birds that previously received numerous opportunities to copulate with a live female quail in the test situation were significantly more likely to copulate with the head?+?neck model than were sexually inexperienced Ss. Exp 3 showed that prior sexual experience with live quail facilitated responding to the head?+?neck model only if the sexual experience was provided in the same place where Ss were later tested with the model. This finding suggests that sexual experience facilitates control of copulatory behavior by species-specific sign stimuli through contextual conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual conditioning with massed versus distributed unconditional stimuli in the absence of explicit conditional stimuli.

Rats received unsignaled shocks in an observation chamber, with different groups varying with respect to time between shocks. Twenty-four hours later the rats were returned to the observation chamber for a test of conditioning to contextual stimuli. The freezing response served as the dependent variable. In Experiment 1 we found that distributed shock trials (60 s) resulted in more context conditioning than did massed trials (3 s or 6 s). Experiment 2 replicated this intertrial interval (ITI) effect when total time in the context was equated for the massed and distributed groups. The observed beneficial effect of distributed practice for conditioning to contextual stimuli runs counter to the predictions of Pavlovian conditioning models that posit that the benefit of distributed conditioning trials for discrete conditional stimuli arises because of decreased contextual conditioning with longer ITIs (e.g., Gibbon & Balsam, 1981; Rescorla & Wagner, 1972). Although the basic effect of enhanced performance with longer ITIs is consistent with Wagner's rehearsal model (e.g., 1978), three findings argue against such an account. First, posttrial stimulation did not reduce the benefit obtained from distributed trials (Experiment 3). Second, intertrial distractors did not improve performance of the animals subjected to massed trials (Experiment 4). And third, the ITI effect was not eliminated when conditioning was brought to its asymptote (Experiment 5). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reduction of prelimbic inhibitory gating of auditory evoked potentials after fear conditioning.

Inhibitory gating (IG) is a basic central nervous system process for filtering repetitive sensory information. Although IG deficits coincide with cognitive and emotional dysfunction in a variety of neuropsychiatric disorders, limited research has been completed on the basic, functional nature of IG. Persistent IG occurs in rat prelimbic medial prefrontal cortex (mPFC), a crucial site for modulating emotional learning. To investigate the interaction of affect and IG, we recorded local field potentials (LFP) directly from prelimbic mPFC and examined the influence of tone-shock fear conditioning (FC) on IG. Behavioral reactions during IG were observed before and after FC, and increase of orienting response after FC indicated induction of tone-shock association. After FC, some components of LFP response exhibited short-term weakening of IG. On a subsequent day of recording, IG strengthened for all LFP components, but individual components differed in their particular changes. Affective regulation of IG represents an important factor influencing within-subject IG variability, and these results have implications for understanding the role of rapid, implicit neural coding involved in emotional learning and affective disruption in psychiatric disease. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual effects in conditioning, latent inhibition, and habituation: Associative and retrieval functions of contextual cues.

Rats were used as subjects in four experiments to investigate the transfer of learning from one context to another. Subjects received two sessions of training each day, one in each of two different contexts. Experiment 1 showed that the habituation of the unconditioned response to a stimulus presented in one context was left intact when the stimulus was presented in another context, but that latent inhibition was attenuated when preexposure and conditioning phases occurred in different contexts. Experiments 2 and 3 demonstrated that a conditioned response made on the basis of an appetitive reinforcer was diminished when conditioning and testing occurred in different contexts, but that aversive conditioning was not influenced by the context in which testing occurred. In Experiment 4, the presence of an aversive reinforcer during training did not preclude the occurrence of context-specific conditioning on the basis of an appetitive reinforcer. Associative and retrieval-based interpretations of the results are explored. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The development of auditory strategies of attention.

Investigated focused and divided attention in right-handed children in 2 age groups: 6.5–7.5 and 10–11 yrs. Ss listened to lists of simultaneous word pairs that were monitored for the presence of designated target words. An analysis of correct and incorrect response rates showed that there was a general increase in the efficiency of both attention tasks with age, although selective listening performance improved to a greater extent than divided attention. In focused attention, selecting one input and ignoring another developed at different rates. In divided attention, there was a right ear advantage that remained constant across the 2 age groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human blink startle during aversive and nonaversive Pavlovian conditioning.

Potentiation of blink startle during aversive and nonaversive Pavlovian single-cue conditioning was assessed in human Ss. In Exp 1 (N?=?89), the conditioning group received paired presentations of a visual CS and an unconditioned stimulus/stimuli (UCS), whereas the control group was presented with a random sequence. The UCS was an electric shock for half the Ss and a nonaversive reaction time (RT) task for the other half. Electrodermal conditioning was evident regardless of the nature of the UCS, but blink potentiation was found only in the conditioning group that had been trained with the aversive UCS. These results were replicated in Exp 2 (N?=?65), in which a nonaversive UCS of increased motivational significance was used. Thus, only aversive conditioning seems to affect the affective valence of the CS, at least as reflected by changes in a skeletal reflex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)