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N K Innis

Publications and source records attributed to N K Innis.

15 recordsLinked to original sources
PubMed1998

Individual differences in radial maze performance and locomotor activity in the meadow vole, Microtus pennsylvanicus.

Individual differences in the radial maze performance and locomotor activity of wild-caught and first-generation laboratory-born meadow voles are described. Based on their patterns of response in an eight-arm radial maze the essentially wild voles fell into three behavioral categories: 1) strict algorithmic (i.e., they systematically chose the next adjacent arm to their previous choice); 2) nonalgorithmic (i.e., they ran the maze without any consistent or definable pattern); and 3) nonrunners (i.e., nonperformers of the task who remained relatively immobile in the arms of the maze). The algorithmic and nonalgorithmic voles further differed in their responses to an interference manipulation of the radial maze task. Algorithmic individuals displayed a marked performance deficit, while the nonalgorithmic individuals showed minimal disruption to a 1-min delay interruption of the maze task. Measurements of several aspects of locomotor activity using the automated Digiscan activity monitoring system revealed that the algorithmic individuals also displayed significantly greater levels of activity than the nonalgorithmic or nonrunners, with no significant difference in activity between the latter two groups. These findings suggest that the algorithmic voles were relatively inflexible in their behavior, while the nonalgorithmic individuals were more flexible in their maze performance and likely in their use of spatial and nonspatial information. These individual differences in laboratory measures of learning behavior and locomotor activity in meadow voles are consistent with the polymorphism that is proposed to occur in the wild.

Animals↗
PubMed1993

Temporal control on interval schedules: what determines the postreinforcement pause?

On fixed-interval or response-initiated delay schedules of reinforcement, the average pause following food presentation is proportional to the interfood interval. Moreover, when a number of intervals of different durations occur in a programmed cyclic series, postreinforcement pauses track the changes in interval value. What controls the duration of postreinforcement pauses under these conditions? Staddon, Wynne, and Higa (1991), in their linear waiting model, propose control by the preceding interfood interval. Another possibility is that delay to reinforcement, signaled by a key peck and/or stimulus change, determines the subsequent pause. The experiments reported here examined the role of these two possible time markers by studying the performance of pigeons under a chained cyclic fixed-interval procedure. The data support the linear waiting model, but suggest that more than the immediately preceding interfood interval plays a role in temporal control.

Animals↗
PubMed1992

Tolman and Tryon. Early research on the inheritance of the ability to learn.

Few psychologists today are aware of the seminal role played by learning theorist Edward C. Tolman in the early development of the field of behavior genetics. Tolman was the first to publish a study of selective breeding for maze-learning ability in rats. He continued to foster research in this field by supporting the work of his students, particularly Robert C. Tryon. Tryon carried out the first major long-term study of maze-bright and maze-dull rats. This article focuses on Tolman's early years at Berkeley and the events culminating in the inheritance project, as well as on the evolution of this research under Tryon's direction.

Animals↗
PubMed1990

Radial maze performance following hippocampal kindling.

The relation between hippocampal epileptiform activity and 8-arm radial maze performance was assessed following repetitive afterdischarges (ADs) evoked by stimulation of the hippocampal CA1 region (kindling). Hippocampal kindling, whether to stage V (generalized) convulsions or to a preconvulsive stage, induced deficits in radial maze performance, evaluated by correct arm entries in 8 choices or total maze run (trial) time. The deficits persisted at least until 21 days after the last AD. Hippocampal interictal spikes (ISs) were induced by kindling, but the rate of ISs declined to near zero in a few days. The rate or presence of ISs was not related to maze performance.

Animals↗
PubMed1989

The role of the hippocampal-nucleus accumbens pathway in radial-arm maze performance.

The role of the glutamatergic hippocampal-nucleus accumbens pathway in relaying hippocampal information via the nucleus accumbens to the motor system was investigated behaviorally using the radial-arm maze paradigm in rats. Bilateral injections of kynurenic acid, a glutamate antagonist, into the nucleus accumbens increased the latency to initiate movement during performance of an 8-arm radial maze with all arms baited and with 4 arms baited. Injections of kynurenic acid did not change the number of visits to previously visited arms (i.e. working memory errors) on both versions of the 8-arm radial maze. However, on the 8-arm radial maze with 4 arms baited, injections increased the number of visits to unbaited arms (i.e. reference memory errors). Similar injections were made in rats with ibotenic acid lesions of the prefrontal cortex in order to eliminate the glutamatergic prefrontal cortex-nucleus accumbens pathway so as to investigate the glutamatergic hippocampal-nucleus accumbens pathway. These rats displayed similar deficits on the radial-arm maze as non-lesioned rats (i.e. enhanced latency to initiate movement and reference memory errors). These findings suggest that the glutamatergic hippocampal-accumbens pathway plays a role in radial-arm maze performance by transferring information required for performing a radial-arm maze to the motor system.

Animals↗
PubMed1986

Interactions between response stereotypy and memory strategies on the eight-arm radial maze.

Three groups of water-deprived rats collected water from the ends of the 8-arm radial maze. Sighted subjects, and subjects blinded either with or without pre-enucleation experience on the radial maze, all retrieved the water efficiently. Most of the subjects exhibited the same response stereotypy, regularly choosing 8 adjacent arms of the maze, then stopping in the center of the maze. The strategies underlying this performance were analysed by interrupting trials and rotating the maze 180 degrees after the subject had made 3 choices. Sighted subjects depended on extramaze stimuli, naive-blind subjects depended on intramaze stimuli and experienced-blind subjects ignored their initial 3 choices after the trial was interrupted. Choice accuracy was equally good whether the subject was returned to the position from which it had been removed, or returned to the opposite side of the central platform. All 3 groups of subjects maintained their stereotyped adjacent-arm responding only as long as such responding was consistent with high choice accuracy. Response stereotypy was prevalent on the radial maze, but response strategies were secondary to memory strategies.

Animals↗
PubMed1986

Behavioral effects of exposure to nuclear magnetic resonance imaging: I. Open-field behavior and passive avoidance learning in rats.

The effect of exposure to the magnetic and radio-frequency fields associated with Nuclear Magnetic Resonance Imaging (MRI) on two standard animal behavior tests, was examined in rats. In the first experiment male rats were given a baseline open-field test and 48 hrs later exposed for 22.5 min to a MRI procedure, a sham imaging procedure, or a control condition. Immediately after this exposure period a second open-field test was administered. All animals were given 4 more daily exposures to their respective treatment conditions and after the last exposure period a third open-field test was given. Analysis of open-field ambulation, rearing, and defecation responses indicated no significant effect of exposure to MRI on these behaviours. In a second experiment rats were conditioned in a step-down passive avoidance task and then exposed for 23.2 min (48 hrs later) to MRI, sham imaging, or control conditions. Retention tests for the passive avoidance response were administered after the first and fifth daily exposure to the experimental treatment conditions. No significant effects of the treatment conditions on retention of the avoidance response were obtained and a third retention test 3 months after the second test, also failed to provide any evidence for treatment effects. These results fail to provide any evidence for short or long term behavioral changes in animals exposed to MRI.

Animals↗
PubMed1986

Behavioral effects of exposure to nuclear magnetic resonance imaging: II. Spatial memory tests.

In order to determine possible effects of exposure to nuclear magnetic resonance imaging (MRI) on cognitive processes, the performance of imaged, sham exposed, and control rats on a spatial memory task was examined. This particular task was chosen because, under some conditions, animals use the magnetic field as a compass when navigating. The rats were required to collect food from eight different locations before returning to an already chosen location. All three groups of rats achieved a high level of performance, and there were no differences between groups in any of the performance measures examined. These results indicate that the MRI procedure has no significant effect on spatial memory processes in rats.

Animals↗
PubMed1983

Behavior induced by periodic food delivery: The effects of interfood interval.

Pigeons were exposed to fixed-time schedules of food presentation ranging from five to 300 seconds. Although consistent, stereotyped response patterns developed during interfood intervals on all schedules, there were distinct differences in the behavior observed on schedules with short, as opposed to long, intervals. During the shorter intervals, responses were performed quite vigorously, a feeder-directed terminal response was observed, and most activities were localized near the feeder. On the longer schedules, no feeder-directed terminal response developed, although the birds were usually near the feeder at the end of intervals. The predominant response involved moving about the chamber, often pacing along one of the walls. Performance during short intervals is accounted for quite well by the antagonistic-motivational state hypothesis suggested by Staddon (1977); however, performance during longer intervals is not. Behavior during interfood intervals may more accurately be classified as reflecting a single (food) motivational state and described simply in terms of Craig's (1918) appetitive behavior.

Journal Article↗
PubMed1978

Contrast effects in multiple fixed-interval reinforcement schedules.

Pigeons were exposed to a multiple fixed-interval one-minute fixed-interval three-minute schedule of reinforcement following training on either a multiple fixed-interval one-minute fixed-interval one-minute schedule or a multiple fixed-interval three-minute fixed-interval three-minute schedule. For all birds, large negative local contrast effects developed during the first of four three-minute intervals in a component; response rate was depressed and postreinforcement pause lengthened in this interval. Positive local contrast effects were evident during the first of 12 one-minute intervals in a component for five of six birds; at asymptote, the pause was very short and response rate slightly elevated during this interval. Overall positive contrast was generally transient and varied considerably across subjects, while overall negative contrast effects, if they occurred, appeared only after a large number of sessions.

Journal Article↗
PubMed1975

Eccentric stimuli on multiple fixed-interval schedules.

The effects of presenting a different ("eccentric") stimulus for one interval during either or both components of a cyclic multiple fixed-interval fixed-interval schedule, with 12 short and four long intervals per cycle, were studied in three experiments. Eccentric stimuli in the short-interval component reliably produced a persistent, substantial elevation in key-peck rate. The effect appears to depend on schedule context and an initial "disinhibiting" effect of the eccentric stimulus.

Journal Article↗
PubMed1971

Temporal tracking on cyclic-interval reinforcement schedules.

Pigeons were exposed to four cycles per session of a schedule in which the duration of successive interreinforcement intervals differed by t-sec. A cycle was composed of seven increasing and seven decreasing intervals, from 2t to 8t sec in length. In Exp. 1, postreinforcement pause tracked interval duration on five cyclic schedules, with values of t ranging from 2 to 40 sec. Tracking was better at shorter t values, and when discriminative stimuli signalled increasing and decreasing parts of the cycle. Pooled data for the whole experiment showed postreinforcement pause to bear a power function relationship to interval length, with a smaller exponent than the comparable function for fixed-interval schedules. Tests in a second experiment showed that pigeons trained on an arithmetic progression could also track schedules in which successive intervals followed either a logarithmic or a geometric progression, although tracking was more stable in the logarithmic case.

Journal Article↗
PubMed1969

Reinforcement omission on fixed-interval schedules.

EXPERIMENTS WITH PIGEONS AND RATS SHOWED THAT: (1) When a brief blackout was presented in lieu of reinforcement at the end of 25% of intervals on a fixed-interval 2-min schedule, response rate was reliably and persistently higher during the following 2-min intervals (omission effect). This effect was largely due to a decrease in time to first response after reinforcement omission. (2) When blackout duration was varied, within sessions, over the range 2 to 32 sec, time to first response was inversely related to the duration of the preceding blackout, for pigeons, and for rats during the first few sessions after the transition from FI 2-min to FI 2-min with reinforcement omission. Post-blackout pause was independent of blackout duration for rats at asymptote. These results were interpreted in terms of differential depressive effects of reinforcement and blackout on subsequent responding.

Journal Article↗