Temporal specificity in cross-modal transfer of the rabbit nictitating membrane response.

Classical conditioning of the nictitating membrane response (NMR) of rabbits is simple associative learning of a motor response. In several two-stage experiments, reversible inactivations of the deep cerebellar nuclei in stage 1 appeared to prevent acquisition of NMR conditioning in naive rabbits no conditioned responses (CRs) were evident after inactivations were lifted in stage 2. Results of a three-stage experiment were different. When subjects were first trained with a light conditional stimulus (CS) in stage 1, reversible cerebellar inactivations during conditioning to a different, tone CS during stage 2 did not appear to prevent new learning because CRs to the tone CS were evident when the inactivation was lifted. Results from the two-stage experiments support the suggestion that the cerebellum is essential for the acquisition of NMR conditioning, but results from the three-stage experiment do not. Here, we use a three-stage design with different interstimulus intervals (ISis) in stages 1 and 2. Because CRs develop with latencies-to-peak dependent on the ISI, learning during stage 1 can be dissociated from that accruing in stage 2. Complete inactivation of the ipsilateral cerebellar nuclei with muscimol substantially but not completely prevented learning with the second ISI during stage 2 because small CR 1Corresponding author. peaks around the stage 2 ISI could be detected in some subjects after the inactivation had been lifted in stage 3. We suggest that the weak levels of conditioning possible during unilateral inactivation depend on the contralateral cerebellum or on extracerebellar circuitry and that these may be capable of supporting transfer of conditioning in a previous three-stage experiment. But, we confirm that normal NMR conditioning is critically dependent on the ipsilateral cerebellum.

Section: Discussionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Acquisition of a new-latency conditioned nictitating membrane response--major, but not complete, dependence on the ipsilateral cerebellum.

Yeo¹,

Lobo²,

Baum³

1997

“…Except for one response to a 6.1-kHz test tone in one animal from group 9.5, no other shortlatency responses were observed (data not shown). Responding was strongest to CS1 and weak or nonexistent to increasingly different test stimuli, generalizing somewhat within the auditory modality but not across modalities (Siegel et al 1968;Liu 1971;Solomon and Moore 1975;Powell and Moore 1980;Holt and Kehoe 1985;Schreurs and Kehoe 1987;Kehoe and Napier 1991;Garcia et al 2003). For group 1.0, CRs occurred mostly to the 1.0-kHz tone and decreased with increasing frequency of test tones (Fig.…”

Section: Stimulus Specificity With Cerebellar Cortex Intactmentioning

confidence: 99%

Stimulus Generalization of Conditioned Eyelid Responses Produced Without Cerebellar Cortex: Implications for Plasticity in the Cerebellar Nuclei

Ohyama

Nores

Mauk³

2003

In Pavlovian eyelid conditioning and adaptation of the vestibulo-ocular reflex, cerebellar cortex lesions fail to completely abolish previously acquired learning, indicating an additional site of plasticity in the deep cerebellar or vestibular nucleus. Three forms of plasticity are known to occur in the deep cerebellar nuclei: formation of new synapses, plasticity at existing synapses, and changes in intrinsic excitability. Only a cell-wide increase in excitability predicts that learning should generalize broadly from a training stimulus to other stimuli capable of supporting learning, whereas the alternatives predict that learning should be relatively specific to the training stimulus. Here we show that deep nucleus plasticity, as assessed by conditioned eyelid responses produced without input from the cerebellar cortex, is relatively specific to the training conditioned stimulus (CS). We trained rabbits to a tone or light CS with periorbital stimulation as the unconditioned stimulus (US), and pharmacologically disconnected the cerebellar cortex during a posttraining generalization test. The short-latency conditioned responses unmasked by this treatment showed strong decrement along the dimension of auditory frequency and did not generalize across stimulus modalities. These results cannot be explained solely by a cell-wide increase in the excitability of deep nucleus neurons, and imply that an input-specific mechanism in the deep cerebellar nucleus operates as well.Several examples of motor learning including Pavlovian eyelid conditioning and adaptation of the vestibulo-ocular reflex require the cerebellum, and the relevant plasticity appears to occur in the cerebellar cortex and the deep cerebellar or vestibular nuclei

“…The observation of rapid transfer from one CS modality to another is not surprising (Kehoe et al 1984;Schreurs and Kehoe 1987;Kehoe and Napier 1991;Campolattaro and Freeman 2009). However, the finding of equivalent transfer from LGNv stimulation to tone and light CSs was unexpected.…”

Section: Discussionmentioning

confidence: 99%

Ventral lateral geniculate input to the medial pons is necessary for visual eyeblink conditioning in rats

Halverson

Freeman²

2010

The conditioned stimulus (CS) pathway that is necessary for visual delay eyeblink conditioning was investigated in the current study. Rats were initially given eyeblink conditioning with stimulation of the ventral nucleus of the lateral geniculate (LGNv) as the CS followed by conditioning with light and tone CSs in separate training phases. Muscimol was infused into the medial pontine nuclei (MPN) after each training phase to examine conditioned response (CR) retention to each CS. The spread of muscimol infusions targeting the MPN was examined with fluorescent muscimol. Muscimol infusions into the MPN resulted in a severe impairment in retention of CRs with the LGNv stimulation and light CSs. A less severe impairment was observed with the tone CS. The results suggest that CS information from the LGNv and light CSs is relayed to the cerebellum through the MPN. Retrograde tracing with fluoro-gold (FG) showed that the LGNv and nucleus of the optic tract have ipsilateral projections to the MPN. Unilateral inputs to the MPN from the LGNv and nucleus of the optic tract may be part of the visual CS pathway that is necessary for visual eyeblink conditioning.The neural substrates of associative motor learning have been studied extensively using eyeblink conditioning (Christian and Thompson 2003;Thompson 2005). Eyeblink conditioning is typically established by pairing a tone or light conditioned stimulus (CS) with an unconditioned stimulus (US) that elicits the eyeblink reflex. An eyeblink conditioned response (CR) emerges over the course of paired training, and the peak of eyelid closure occurs at the onset time of the US. Results from experiments using temporary lesions of the cerebellar deep nuclei or cerebellar cortex indicate that the anterior interpositus nucleus and cerebellar cortex are necessary for acquisition, expression, and extinction of eyeblink conditioning (Krupa et