I. Gormezano

Nictitating membrane: classical conditioning and extinction in the albino rabbit.

The distribution of response latencies and the percentage performance curve of a classical conditioning group, by comparison with a control group, indicated that the extension of the nictitating membrane elicited by a puff of air to the cornea was successfully conditioned to a previously neutral stimulus.

Microprocessor control and A/D data acquisition in classical conditioning

An Apple II/FIRST system has been developed to control classical conditioning experiments, collect analog data, and to extract dependent variable measures of conditioning. With our selection of the Apple II microprocessor and an added hardware floating-point processor, we have been able to establish independent computer systems for each of our three conditioning laboratories at a fraction of the cost of our DEC PDP-8/e (which was interfaced to only one of our laboratories). Moreover, our software system, FIRST, an interactive, high-level, dictionary-based language, is a programming and control system whose flexibility and ease of programming far exceeds that experienced with our DEC PDP-8/e system (Millenson, Kehoe, Tait, á Gormezano, 1973; Tait & Gormezano, 1974). In our judgment, the Apple II/FIRST system is of unprecedented efficiency and versatility for the control, data acquisition, and data analysis of analog responses in classical conditioning experiments.

Classical conditioning of the rabbit's nictitating membrane response under fixed and mixed CS-US intervals

Abstract The rabbits nictitating membrane response was classically conditioned to a tone CS, followed by an electric shock US, at two randomly alternating CS-US interstimulus intervals (ISIs). Different groups were exposed to different proportions of 200- and 700-msec ISIs. The study revealed: (a) CR percentage was a direct function of the proportion of 200-msec ISIs; (b) trials to the first test-trial CR were an inverse function of the proportion of 200-msec ISIs; (c) CR onset latencies decreased over training; (d) CR peak latencies coincided with the temporal loci of the US; and (e) groups exposed to both ISIs acquired double-peaked CRs. Moreover, the amplitudes of nictitating membrane responses in the present experiment paralleled certain quantitative aspects of the free operant key peck response rates of pigeons trained under two mixed inter-reinforcement intervals. The results were discussed with respect to the micromolar response shaping and macromolecular CS-trace accounts of classical conditioning.

Acquisition and extinction of the classically conditioned eyelid response in the albino rabbit.

Comparisons of the performance curve of a classical conditioning group with the curves of control groups provided unequivocal evidence that elicitation of eyelid responses to the conditioned stimulus was acquired by associations formed between the conditioned stimulus and the unconditioned stimulus.

Transduction of the rabbit's nictitating membrane response

Gormezano, Schneiderman, Deaux, and Fuentes (1962) introduced the rabbit nictitating membrane response (NMR) preparation and the use of a minitorque rotary potentiometer and hook and thread for NM coupling that, over the ensuing years, has remained the almost universally employed method of NMR measruement (see Gormezano, Prokasy, & Thompson, 1987). However, in recent years, our laboratory has been employing a photoresistive Polaroid transducer and ball-joint NM coupler that, in our judgment, has many advantages over any extant method of NMR measurement. The present paper provides a description of the design and functional properties of the transducer and coupler.

Differential conditioning of the rabbit's nictitating membrane response to serial compound stimuli.

Three experiments were conducted to determine the time course and contents of CS representations through an examination of differential conditioning of the rabbits nictitating membrane response to two serial compounds. One compound (A-X+) was always paired with the unconditioned stimulus, and the other (B-X-) was always presented alone. All three experiments entailed manipulation of the interstimulus interval between the initial distinctive element of each compound (A and B) and the second, shared element (X). The joint results revealed that (a) conditioned response acquisition to the initial elements depended on the presence of X in the A-X+ compound; (b) differentiation between A and B appeared across interstimulus intervals up to 4,600 ms; and (c) conditional control over responding following A and B appeared at interstimulus intervals of at least 4,600 ms and perhaps up to 12,600 ms. The results are discussed with respect to mechanisms of occasion setting, generalization, and configuration.

Localization of retractor bulbi motoneurons in the rabbit

Motoneurons innervating the rabbit retractor bulbi muscle have been identified by retrograde transport of horseradish peroxidase (HRP). Following injection of HRP into single slips or all 4 slips of the retractor bulbi muscle, labeled motoneurons were consistently observed in the abducens (ABD) nucleus and in the accessory abducens (ACC) nucleus located ventral, lateral and rostral to the ABD. Axons from the ACC motoneurons could be seen to enter the VIth nerve. Injection of HRP into the lateral rectus muscle produced consistent labeling of motoneurons in the ABD nucleus overlapping the distribution of retractor bulbi motoneurons, but labeling was never observed in the ACC nucleus. The number of labeled ABD neurons after lateral rectus injections was far less (36%) than after injection into all 4 slips of the retractor bulbi muscle (72%). Injection of HRP into the superior oblique, superior rectus or medial rectus muscle produced labeling of motoneurons in the corresponding subdivisions of the oculomotor nucleus or trochlear nucleus but no labeled motoneurons were observed in either the ABD or ACC nuclei. Some highly inconsistent labeling of oculomotor nucleus was observed after retractor bulbi or lateral rectus muscle injections and this was judged to be due to intraorbital diffusion of the HRP. It was concluded that the retractor bulbi muscle is innervated by motoneurons located in both the ABD and ACC nuclei.

Heart rate classical conditioning in rabbits

Comparisons of heart rate changes between experimental groups receiving paired presentations of tone (CS) and shock (US) and control groups that did not, indicated that conditioned responses occurred within 10 CS-US pairings, and were decelerative with latencies less than.5 sec. and durations of 8 sec. or more.

Associative transfer and stimulus selection in classical conditioning of the rabbit's nictitating membrane response to serial compound CSs.

Four experiments were conducted to determine whether in conditioning to a serial compound, CS1-CS2-UCS, there are (a) associative mechanisms operating to extend conditioning beyond the bounds of a CS-UCS contiguity gradient and (b) stimulus selection processes acting to attenuate the potency of CS-UCS contiguity. In Experiments 1 and 2, the CS2-UCS interval was held at .35 sec while the CS1-UCS interval was varied across groups from .75 to 2.75 sec. CS1 test trials revealed substantial CR acquisition at all CS1-UCS intervals. Moreover, Experiment 2 indicated that when the contribution of cross-modal generalization from CS2 to CS1 was factored out, there still remained a substantial level of conditioning, which Experiment 3 indicated was attributable to an associative mechanism like higher-order or sensory conditioning. The observation of CR acquisition at CS1-UCS intervals of 4.75, 8.75, and 18.75 sec in Experiment 4 suggested that serial compound training yields conditioning to CSs located well beyond the single CS contiguity gradient for the rabbits nictitating membrane response. Experiments 1 and 2 also indicated the presence of stimulus selection processes because, at the shorter CS1-UCS intervals (.75 and 1.25 sec), the levels of test-trial responding to CS2 fell below those observed to the less contiguous CS1.

CS Intensity effects on rabbit nictitating membrane conditioning, extinction and generalization

One purpose of the present experiments was to determine if the Grice and Hunter (1964) observation of augmented within-versus between-Ss CS intensity effects in human eyelid conditioning would be obtained in conditioning of the rabbit’s nictitating membrane response under two (Experiment 1) and four (Experiment 2) CS intensity values. In addition, a determination was made of the effects of CS intensity upon extinction and stimulus intensity generalization gradients. The studies revealed that: (a) while acquisition performance was positively related to CS intensity, the effect was independent of the between and within-S manipulation of CS intensity; (b) rate of response decrement in extinction was an inverse function of CS intensity; and (c) a positively sloped intensity generalization gradient was obtained when the training stimulus was the low-intensity one. Overall, these results are most consistent with Hull’s (1949) stimulus intensity dynamism account of CS intensity effects in conditioning.