Jonathan M. Reed

Recognition Memory and the Human Hippocampus

The capacity for declarative memory depends on the hippocampal region and adjacent cortex within the medial temporal lobe. One of the most widely studied examples of declarative memory is the capacity to recognize recently encountered material as familiar, but uncertainty remains about whether intact recognition memory depends on the hippocampal region itself and, if so, what the nature of the hippocampal contribution might be. Seven patients with bilateral damage thought to be limited primarily to the hippocampal region were impaired on three standard tests of recognition memory. In addition, the patients were impaired to a similar extent at Remembering and Knowing, measures of the two processes thought to support recognition performance: the ability to remember the learning episode (episodic recollection) and the capacity for judging items as familiar (familiarity).

Assessing implicit learning with indirect tests: Determining what is learned about sequence structure.

These studies investigated the unconfounding of learning of simple frequency information from complex structure during sequenced serial reaction time (RT) trials. Experiment 1 demonstrated that disruptions in RTs that occur when Ss are transferred to random trials (e.g., A. Cohen, R. Ivry, & S. W. Keele, 1990) may result from a change in simple frequency information. The implication is that negative transfer effects cannot be attributed to the learning of complex information if simpler information is also allowed to vary between training and transfer trials. Experiment 2 used a procedure in which simple frequency information remained constant between training and transfer trials, which provided evidence of complex sequence structure learning while subjects were engaged in a secondary tone-counting task

Impaired Recognition Memory in Patients With Lesions Limited to the Hippocampal Formation

A recent literature survey of results from a widely used recognition memory test raised questions about the extent to which recognition memory impairment ordinarily occurs in human amnesia and, in particular, whether recognition memory is impaired at all after damage limited to the hippocampal region (J. P. Aggleton & C. Shaw, 1996). Experiment 1 examined the performance of 6 amnesic patients on 11 to 25 different recognition memory tests. Three patients had bilateral lesions limited primarily to the hippocampus (G.D.) or the hippocampal formation (W.H. and L.M.), as determined by postmortem, neurohistological analysis (N. Rempel-Clower, S. M. Zola, L. R. Squire, & D. G. Amaral, 1996). All 6 patients exhibited unequivocally impaired recognition memory. In Experiment 2, the 3 patients still available for study were each markedly impaired on a test of object recognition similar to the kind used to test recognition memory in nonhuman primates. Recognition memory impairment is a robust feature of human amnesia, even when damage is limited primarily to the hippocampus.

Prenatal stress and prepuberal social rearing conditions interact to determine sexual behavior in male rats

The two major categories of factors known to influence adult sexual behavior potentials are the relative amounts of androgen present during specific stages of perinatal ontogeny and adequate social stimulation during prepuberal development. The possible interaction between these two was evaluated by characterizing the ejaculatory and lordotic behavior potentials of prenatally stressed and control male rats that had been weaned at 16 days of age and raised either in total social isolation or with a same-age female, a control male, or a prenatally stressed male. The decrement in male sexual behavior produced by prenatal stress was attenuated by raising the male with either a female or a control male. Social isolation alone or in combination with stress resulted in severely deficient male behavior. Peripheral skin shock promoted ejaculatory behavior in many previously noncopulating prenatally stressed males raised with other stressed males, but it was ineffective in most isolated animals. The high lordosis potential characteristic of prenatally stressed male rats was slightly lower in the group with a female cagemate and was markedly decreased by social isolation. These results support and extend the finding by Dunlap, Zadina, and Gougis (1978) that prenatal hormonal events and prepuberal rearing conditions can interact to attenuate or accentuate the effects that either treatment alone has on the development of adult sexual behavior potentials.

Impaired transverse patterning in human amnesia is a special case of impaired memory for two-choice discrimination tasks.

Three amnesic patients with damage limited to the hippocampal formation, a severely amnesic patient with extensive medial temporal lobe damage, and 9 controls were tested on the transverse patterning problem (A + B-, B + C-, and C + A-) and also on 2 control problems. One of the control problems was matched to the transverse patterning problem with respect to the number of pairwise decisions that were required. The 2nd control problem was matched to the transverse patterning problem with respect to the number of trials needed by controls to learn the task. The amnesic patients were impaired at solving both the transverse patterning problem and the control problems. The findings suggest that impaired learning of the transverse patterning problem by amnesic patients derives from their general impairment in declarative memory, which affects performance on most 2-choice discrimination tasks.

When Amnesic Patients Perform Well on Recognition Memory Tests

Extended exposure to study material can markedly improve subsequent recognition memory performance in amnesic patients, even the densely amnesic patient H.M. To understand this phenomenon, the severely amnesic patient E.P., 3 other amnesic patients, and controls studied pictorial material and then were given either a yes-no (Experiment 1) or a 2-alternative, forced-choice (Experiment 2) recognition test. The amnesic patients and controls benefited substantially from extended exposure, but patient E.P. consistently performed at chance. Furthermore, confidence ratings corresponded to recognition accuracy. The results do not support the idea that the benefit of extended study time is due to some kind of familiarity process made available through nondeclarative memory. It is likely that amnesic patients benefit from extended study time to the extent that they have residual capacity for declarative memory.

What makes targets redundant

Two letter-classification experiments that investigated target-redundancy effects on reaction time (RT) were conducted. Both experiments were replicated with choice reaction time (CRT) and go/no-go (GNG) procedures. In each experiment, there were two single-target conditions, one with a noise letter and one without. In one experiment, the letter classes were two letters that could be of either case. In the second experiment, each class consisted of two different capital letters. In both experiments, there were two redundant-targets conditions, one with identical targets and one with the different members of a class. In both of the GNG experiments, redundancy gains were obtained comparing the different-targets condition with the no-noise, single-target condition. Redundant stimuli are ones that lead to the same response. Visually different stimuli may be processed in parallel and jointly activate a response. GNG procedures are more sensitive than CRT in the investigation of redundancy effects.

Potential Clinical Implications of Implicit and Explicit Attitudes Within Possible Exercise Selves Schemata: A Pilot Study

Our purpose was to explore implicit as well as explicit exercise schemata of 51 inactive to highly active college students. For the implicit measure, a pilot study was used to establish the word set (exercise-related, nonexercise-related, and nonwords) for the lexical decision task. A latency differential was calculated based on reaction times to these word sets. Participants used self-regulatory functions to rate both hoped and feared exercise selves and reported workout hours. An estimate of aerobic fitness was derived. Results showed that implicit exercise attitudes were related to the “importance” placed on being an exerciser and on avoiding being a nonexerciser. Those who self-identified as an exerciser had higher levels of self-efficacy, workouts, and fitness. In contrast, those who self-identified as a nonexerciser were less active and fit and seemed to dwell on negative thoughts related to self-efficacy. Clinicians might help clients explore these attitudes, especially importance.

Short-term incidental memory for irrelevant cues.

A new analysis of previously published studies of delayed matching-to-sample (DMTS) water-escape and the results of a new food-reinforced discrimination study are presented. In both cases, male Sprague-Dawley rats demonstrated short-term incidental memory for irrelevant cues in the context of two-alternative forced-choice problems that required learning about relevant cues. In the DMTS experiments, relevant and irrelevant cues were place or brightness. In the discrimination experiment, the relevant cues were place, brightness or a visual-tactile maze insert. In all experiments, after the rats attained high-level performance, consistently making choices with respect to the relevant stimuli, response latencies to the correct relevant cue were shorter when the irrelevant cue value(s) was the same as on the immediately preceding trial. These latency differences are interpreted as indicating that the rats demonstrated short-term incidental memory for the irrelevant cues. This mnemonic phenomenon resembles priming, an implicit form of memory.