Temporal discrimination using different feature-target intervals in classical conditioning of the rabbit’s nictitating membrane response

The cerebellar anterior lobe may play a critical role in the execution and proper timing of learned responses. The current study was designed to monitor Purkinje cell activity in the rabbit cerebellar anterior lobe after eyeblink conditioning, and to assess whether Purkinje cells in recording locations may project to the interpositus nucleus. Rabbits were trained in an interstimulus interval discrimination procedure in which one tone signaled a 250-msec conditioned stimulus-unconditioned stimulus (CS-US) interval and a second tone signaled a 750-msec CS-US interval. All rabbits showed conditioned responses to each CS with mean onset and peak latencies that coincided with the CS-US interval. Many anterior lobe Purkinje cells showed significant learning-related activity after eyeblink conditioning to one or both of the CSs. More Purkinje cells responded with inhibition than with excitation to CS presentation. In addition, when the firing patterns of all conditioning-related Purkinje cells were pooled, it appeared that the population showed a pattern of excitation followed by inhibition during the CS-US interval. Using cholera toxin-conjugated horseradish peroxidase, Purkinje cells in recording areas were found to project to the interpositus nucleus. These data support previous studies that have suggested a role for the anterior cerebellar cortex in eyeblink conditioning as well as models of cerebellar-mediated CR timing that postulate that Purkinje cell activity inhibits conditioned response (CR) generation during the early portion of a trial by inhibiting the deep cerebellar nuclei and permits CR generation during the later portion of a trial through disinhibition of the cerebellar nuclei.Eyeblink classical conditioning has been used with great success to study the involvement of the cerebellum in motor learning. In eyeblink conditioning, a conditioned stimulus (CS), usually a tone, precedes an unconditioned stimulus (US), usually a corneal air puff, by 250-750 msec. Initially, the air puff US elicits a reliable response, in the form of a reflexive eye blink that is called an unconditioned response (UR). Over the course of a few hundred paired CS-US trials, an eye blink to the CS develops, which has a longer latency than the UR and differs in topography. This learned response is called the conditioned response (CR). One of the deep cerebellar nuclei, the interpositus nucleus, appears to be critical for learning CRs during eyeblink conditioning (e.g., Lavond et al. 1985;Yeo et al. 1985a;). In addition, lesions of some regions of cerebellar cortex (i.e., Larsell's lobule HVI) have been reported to affect CR production (e.g., Yeo et al. 1985b;Lavond and Steinmetz 1989) and recordings of Purkinje cell activity in this area have revealed inhibitory and excitatory patterns of activity that appear to be related to CS or US presentation and CR execution (e.g., Berthier and Moore 1986; Katz and Steinmetz 1997).Mauk and colleagues have presented data suggesting that another region of the cerebellar cortex, the cerebellar a...

Section: Discussionsupporting

confidence: 82%

“…Onset and peak latencies were calculated from CR trials only. Double-peaked CRs were defined as CRs with an initial peak of at least 1.0-mm, followed by a retraction of at least 1.0-mm, followed by a second peak of at least 1.0-mm (Kehoe et al 1993).…”

Section: Discussionmentioning

confidence: 99%

Purkinje cell activity in the cerebellar anterior lobe after rabbit eyeblink conditioning

Green¹,

Steinmetz²

2005

“…Although they did not appear to play a role in the present results, the rabbit NM response is sensitive to both the global context provided by the apparatus cues (Hinson 1982;Kim 1986;Saladin and Tait 1986;Kehoe et al 2004;Poulos et al 2004) and conditional cues (occasion-setters) that have ranged up to a minute in length (Macrae and Kehoe 1995;Weidemann and Kehoe 1997;Rogers and Steinmetz 1998;Kehoe and Boesenberg 2002). Furthermore, the US-related internal context has the potential to make a contribution.…”

Section: Discussionmentioning

confidence: 59%

Repeated acquisitions and extinctions in classical conditioning of the rabbit nictitating membrane response

Kehoe

2006

The rabbit nictitating membrane (NM) response underwent successive stages of acquisition and extinction training in both delay (Experiment 1) and trace (Experiment 2) classical conditioning. In both cases, successive acquisitions became progressively faster, although the largest, most reliable acceleration occurred between the first and second acquisition. Successive extinctions were similar in rate. The results challenge contextual control theories of extinction but are consistent with attentional and layered-network models. The results are discussed with respect to their implications for the interaction between cerebellar and forebrain pathways for eyeblink conditioning.The present experiments were aimed at resolving three questions concerning the effect of repeated cycles of acquisition and extinction training in the rabbit nictitating (NM) preparation.First, it is uncertain whether successive acquisitions and extinctions become faster or slower. Previous studies using the rabbit NM preparation have not yielded conclusive findings (Smith and Gormezano 1965;Scavio and Thompson 1979). In the two older studies, single sessions of acquisition training were alternated with single sessions of extinction training. After the first cycle of acquisition and extinction sessions, reacquisition was virtually instantaneous and showed no changes over successive cycles. The rate of extinction, on the other hand, appeared to accelerate over successive cycles. Similarly, Scavio and Thompson (1979) observed uniformly rapid reacquisition and accelerated extinction when they used three or more sessions of extinction in each cycle. In all three studies, however, the extinction sessions did not entirely abolish responding, and they would not have abolished spontaneous recovery, which is pronounced in the rabbit NM preparation (Haberlandt et al.

“…First, the use of multiple-stimuli paradigms has a long history in behavioral neuroscience (e.g., Hall and Minor 1984;Bellingham et al 1985;Kehoe et al 1993) and is generally thought to involve the same processes as single-stimulus training. Second, the results of the within-subject, permanent lesion experiment upon which we based our paradigm (Purves et al 1995) were essentially identical to those of a between-subject experiment that also used permanent lesions (Reilly et al 1993).…”

Section: Discussionmentioning

confidence: 99%

Hippocampal inactivation enhances taste learning

Stone¹,

Grimes²,

Katz³

2005

Learning tasks are typically thought to be either hippocampal-dependent (impaired by hippocampal lesions) or hippocampal-independent (indifferent to hippocampal lesions). Here, we show that conditioned taste aversion (CTA) learning fits into neither of these categories. Rats were trained to avoid two taste stimuli, one novel and one familiar. Muscimol infused through surgically implanted intracranial cannulae temporarily inactivated the dorsal hippocampus during familiarization, subsequent CTA training, or both. As shown previously, hippocampal inactivation during familiarization enhanced the effect of that familiarization on learning (i.e., hippocampal inactivation enhanced latent inhibition of CTA); more novel and surprising, however, was the finding that hippocampal inactivation during training sessions strongly enhanced CTA learning itself. These phenomena were not caused by specific aspects of our infusion technique-muscimol infusions into the hippocampus during familiarization sessions did not cause CTAs, muscimol infusions into gustatory cortex caused the expected attenuation of CTA, and hippocampal inactivation caused the expected attenuation of spatial learning. Thus, we suggest that hippocampal memory processes interfere with the specific learning mechanisms underlying CTA, and more generally that multiple memory systems do not operate independently.