In a now classic study, W. J. Brogden and W. H. Gantt (1942, American Journal of Physiology, 119, 277-278) demonstrated that movements (limbs, head, eyelid) elicited by direct electrical stimulation of certain regions of the cerebellum (particularly the ansiform lobe) could be trained to respond to neutral auditory or visual conditioned stimuli with appropriate pairing. In recent work we have replicated these results in detail and presented considerable evidence that the reinforcing or "teaching" pathway so activated for the learning of discrete movements is the inferior olive-climbing fiber projection system to the cerebellum. Very strong evidence now indicates that the memory traces for this "skilled response" learning are formed and stored in the cerebellum. The climbing fiber system and inhibitory pathway from the interpositus nucleus to the inferior olive appear to form a neural instantiation of the Resorla-Wagner formulation of classical conditioning and accounts for the "cognitive" phenomenon of blocking. It is concluded that reinforcement in this form of learning is not due simply to contiguity/contingency or to unconditioned stimulus aversiveness, per se, but rather to activation of a particular brain circuit, here the climbing fiber system, a circumstance that may apply to other forms of learning, with other reinforcement circuits, as well.

Animals↗

PubMedDate not supplied

Cerebral substrates of Pavlovian conditioning of discrete behavioral responses.

Explore the source record for details and available documents.

Animals↗

PubMedDate not supplied

Classical conditioning in 3-, 30-, and 45-month-old rabbits: behavioral learning and hippocampal unit activity.

Evidence has accumulated to suggest that the hippocampus is impaired by aging processes. Hippocampal multiple unit activity was examined in 3-, 30-, and 45-month-old rabbits during classical conditioning in the trace paradigm. Animals were trained daily with 126 paired trials of tone and airpuff. The 3-month-olds learned to a criterion of 8/9 CR's in a mean of 3.2 days, while the 30-month-olds took a mean of 9.4 days, and the 45-month-olds took a mean of 11.75 days. Neural unit activity in the hippocampus modeled the behavioral eyelid response but took much longer to develop in the older animals. Results suggest that rabbits as young as 2 1/2 years old show behavioral and correlated neural response deficits.

Aging↗

PubMedDate not supplied

The effects of age on eyeblink conditioning in the freely moving Fischer-344 rat.

The effects of age were assessed on the ability of male Fischer-344 rats to acquire a classically conditioned eyeblink using the "delay" paradigm. Using a 350 ms white noise conditioning stimulus and a 100 ms coterminating periorbital shock (2 mA, 60 Hz, AC) we have demonstrated that these rats exhibit deficits as early as middle age. Middle-aged and senescent rats (18 and 30 months) exhibited significantly fewer conditioned responses than young rats (3 and 12 months). Since all of the rats responded to a test noise, and there were no differences in threshold to evoke a blink, this result is likely to be due to an associative deficit. Thus, our results indicate that eyeblink conditioning in the freely moving rat is a useful model system for behavioral and neurobiological analyses of the effects of age on associative learning and memory.

Aging↗

PubMedDate not supplied

Delayed acquisition of eyeblink conditioning in aged F1 hybrid (Fischer-344 x Brown Norway) rats.

We previously reported that the freely moving male Fischer-344 rat provides a useful model to demonstrate the progressive impairment of eyeblink conditioning associated with aging. However, because the youngest F-344 rats only performed at 60% of maximum, we ran the same experiment with hybrid rats and discovered most (i.e., those age 9-24 months) learned rapidly and exhibited conditioned responses on greater than 80% of trials by the end of two training sessions. In contrast, the aged rats (36 months) exhibited significantly fewer CRs on all four training days. However, unlike all ages of F-344 rats (3-30 months) which were run in our last study, these aged hybrid rats exhibited considerable improvement with extra training. These data indicate clear differences in the rate of learning between the two strains and suggest that even young F-344 rats may have deficits in the neural circuits which mediate eyeblink conditioning. Other anecdotal findings on differences between the two strains are noted.

Aging↗

PubMedDate not supplied

Analysis of temporal relations among units and slow waves in rabbit hippocampus.

Arrays of triple microelectrodes were stereotaxically lowered into CA1, CA3 and dentate areas of the dorsal hippocampal formation in anesthetized rabbits. Recordings of action potentials and waves were analyzed on a PDP-11 computer using auto-, cross-, and multiple-correlation programs to determine temporal relations during 90 sec samples of spontaneous activity. It was found that temporal periods of neuronal firing and inhibition were strongly related to the pattern of waves. During periods of high amplitude synchronous waves (theta), the correlation between the activities of different groups of neurons was directly related to the periodicity of the wave. During instances of lower amplitude, desynchronous wave activity, the correlations between spikes recorded from those same cells were less periodic, varying according to the amount of wave synchrony. Variations in wave synchrony due to anatomical location, eserine effects, or spontaneous fluctuations under anesthesia produced corresponding variations in the relations between the activities of different groups of neurons. It is suggested that these relations between neuronal activity and gross waves may be implicated in processes which are at the basis of learning and memory.

Anesthesia↗

PubMedDate not supplied

Classical conditioning of rabbits 2-1/2 to 4 years old using mossy fiber stimulation as a CS.

A basic issue in age-related deterioration in memory formation concerns the locus of the age changes. Changes in peripheral portions of the auditory CS pathway could account for the observed age differences in classical conditioning in rabbits. We bypassed peripheral portions of the CS pathway and input the CS more centrally by electrical microstimulation of mossy fibers in the pons. New Zealand White rabbits aged 2-1/2-4 years were compared to six 3-month-old control rabbits with electrode implantations in comparable areas. Training consisted of 108 trials per day in which stimulation CS was paired with a corneal airpuff US. Older rabbits took almost five times as long to condition as the young animals. Thus, age differences in eyelid classical conditioning cannot be entirely attributed to changes in the peripheral CS pathway. Changes in the nervous system occurring more centrally in the cerebellum appear to affect learning and memory.

Acoustic Stimulation↗