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At least 631 records · Page 35Linked to original sources
PubMed2006

Recency effects in HIV-associated dementia are characterized by deficient encoding.

The aim of the present study was to investigate the nature and cognitive mechanisms of serial position learning effects in HIV-associated dementia (HAD). Participants were 16 persons with HAD, 50 non-demented persons with HIV-infection, and 50 demographically comparable HIV-seronegative participants. HAD participants, relative to both comparison groups, exhibited reduced middle region (p<0.01) and elevated recency region (p<0.05) recall on the Hopkins Verbal Learning Test-Revised, but no primacy region effect (p>0.10). On recognition testing, the HAD group was impaired in discriminating targets from distractors (p<0.01) in all three serial position regions; however, they were not impaired on measures of retrieval (p>0.10) within these same regions. In sum, HAD participants relied disproportionately on recency regions of the list, indicating a passive recall style of echoing only the words within their auditory attention span. Interestingly, HAD participants did not evidence significant improvement on measures of recognition, a finding that suggests that the serial position effects are most consistent with a primary encoding deficit.

AIDS Dementia Complex↗
PubMed1991

Memory for temporal order in schizophrenia.

Memory for temporal order information was examined in patients with chronic schizophrenia using the recency discrimination task. In this task, subjects were shown a pair of previously studied words and were asked to choose which one of the two words they had seen more recently. In addition, subjects performed the Wisconsin Card Sorting Test (WCST). The results showed that schizophrenic patients differed from normal control subjects in their performance on the recency discrimination task. In addition, for schizophrenic patients, performance on the recency discrimination task was inversely related to the number of perseverative errors on the WCST. These results provide further evidence of prefrontal-type cognitive deficits in schizophrenia.

Adult↗
PubMed1994

Aetiological variation in the amnesic syndrome: comparisons using the list discrimination task.

In this study, the performance of amnesic patients with presumed temporal lobe damage was compared with that of patients with presumed diencephalic damage using the temporal list discrimination task. The two patient groups performed similarly on a measure of recognition, but the diencephalic group was impaired relative to the temporal lobe group on a measure of temporal discrimination. Discrimination performance in the temporal lobe group was significantly correlated with recognition memory. The data are interpreted as showing a qualitative difference in the form of amnesia arising from damage centred on the medial temporal lobes compared with that centred on the midline diencephalon.

Adult↗
PubMed1994

The effects of lesions to the fornix and dorsomedial thalamus on concurrent discrimination learning by rats.

Rats with lesions in either the fornix or the thalamic nucleus medialis dorsalis were unimpaired on the acquisition of two object discrimination tasks. The same animals were then tested on a concurrent learning task in which various object discriminations were presented at different rates during the same session. This arrangement was primarily designed to minimise any response bias effects. Animals were able to acquire the various concurrent tasks, even when only one trial per day was given for a particular discrimination. It was found that fornix lesions had little or no effect and only produced a mild impairment when the rate of stimulus presentation resembled that used in typical concurrent tasks. Lesions of medialis dorsalis produced a more general, but again mild, deficit. In a final task, the animals were trained to discriminate between two stimuli composed of common elements arranged in different spatial combinations. Fornix lesions impaired acquisition of this spatial configural discrimination, while lesions of medialis dorsalis had a variable effect. The results indicate that fornix lesions can spare concurrent discrimination learning, and that any deficits may be related to interference effects associated with common elements in the stimuli. Lesions in medialis dorsalis appear to affect the initial learning of reward-based performance rules.

Animals↗
PubMed2005

Orientation-invariant object recognition: evidence from repetition blindness.

The question of whether object recognition is orientation-invariant or orientation-dependent was investigated using a repetition blindness (RB) paradigm. In RB, the second occurrence of a repeated stimulus is less likely to be reported, compared to the occurrence of a different stimulus, if it occurs within a short time of the first presentation. This failure is usually interpreted as a difficulty in assigning two separate episodic tokens to the same visual type. Thus, RB can provide useful information about which representations are treated as the same by the visual system. Two experiments tested whether RB occurs for repeated objects that were either in identical orientations, or differed by 30, 60, 90, or 180 degrees . Significant RB was found for all orientation differences, consistent with the existence of orientation-invariant object representations. However, under some circumstances, RB was reduced or even eliminated when the repeated object was rotated by 180 degrees , suggesting easier individuation of the repeated objects in this case. A third experiment confirmed that the upside-down orientation is processed more easily than other rotated orientations. The results indicate that, although object identity can be determined independently of orientation, orientation plays an important role in establishing distinct episodic representations of a repeated object, thus enabling one to report them as separate events.

Adult↗
PubMed2001

Involvement of the dorsal anterior cingulate cortex in temporal behavioral sequencing: subregional analysis of the medial prefrontal cortex in rat.

We recently demonstrated that rats with dorsal anterior cingulate (ACd) cortical lesions were disrupted in the acquisition of a temporal Go/No-Go alternation task, suggesting either an involvement of this medial prefrontal subregion in sequencing temporally ordered behaviors or alternatively in more general response selection processes 'Gisquet-Verrier et al., Psychobiology 28 (2000) 248'. In the present study, the effects of ACd lesions were investigated in two different training situations. Both tasks involved response selection but only one of the two tasks required behavioral sequencing. In experiment 1, rats with ACd lesions were normally able to select Go and No-Go responses, when selection processes were based on a tone/light conditional rule that does not require temporal patterning. In experiment 2, ACd-lesioned rats were disrupted during the acquisition of a spatial alternation task that relies on temporal patterning. These results provide further evidence of ACd involvement in behavioral sequencing, regardless of the nature (spatial or non-spatial) of chained responses. A comparison of ACd lesions-induced effects with those obtained with lesions to the adjacent prelimbic-infralimbic area 'Delatour & Gisquet-Verrier, Behav. Neurosci. 110 (1996) 1282; Delatour & Gisquet-Verrier, Behav. Neurosci. 113 (1999) 941' reveals a double dissociation of these two regions that reflects a functional regionalization of the medial prefrontal cortex in the rat.

Animals↗
PubMed2005

A new mathematical model for assessment of memorization dynamics.

A new memory model is proposed based on regression analysis and exponential- shaped learning curves. The efficacy of the model is tested with several types of experiments including food aversion in snails, maze learning in rats and memory tests for adults and children. The model is also tested on drug abusers and alcoholics. The results of goodness of fit tests indicate that our model can accurately be used to predict the memory dynamics of diverse experiments and populations. The model can also be used to predict both group and individual performance. The application of the model to detect memory impairment is discussed, as are limitations.

Adult↗
PubMed1989

Dissociation of item and order memory following parietal cortex lesions in the rat.

Rats with parietal cortex lesions were tested for both item and order memory for a list of spatial events in a probe recognition procedure. Rats with parietal cortex lesions were impaired for all events within the item memory task but had good memory for the early events within the order memory task. These data suggest a dissociation of function between item and order memory for parietal cortex damaged animals. In conjunction with previous findings with rats with medial prefrontal cortex lesions, these data suggest that item and order memory can be coded and represented independently.

Animals↗
PubMed1989

Further studies of hippocampal representation during odor discrimination learning.

The contribution of hippocampal and nonhippocampal memory processing to simultaneous-cue odor discrimination learning was assessed. In this task, rats with hippocampal system damage consequent to fornix lesions (fornix rats) were severely and persistently impaired in discrimination learning, acquisition of learning set, and concurrent discrimination, although they occasionally solved some problems at a normal rate. By using those problems on which fornix rats succeeded, to permit comparisons of performance strategies with normal rats, differences between groups were shown on response latency measures and on probe trials involving the novel pairing of familiar odors. Normal rats had a bimodal distribution of response latencies, and their latency depended on where the S+ was presented. Fornix rats had short response latencies and responded equally quickly wherever the S+ was presented. Furthermore, when the representation of familiar S+ and S- odor pairs was challenged in probe trials, normal rats responded appropriately to the correct stimulus, whereas fornix rats behaved as if presented with a new odor pair. These data provide support for the view that the hippocampus participates in the representation of relations among odor (and other) stimuli and among other experiences and that it permits the flexible use of these representations in new contexts. In contrast, memory processing outside the hippocampal system can represent only the significance of individual stimuli and can be revealed only in a repetition of the original learning event.

Animals↗
PubMed2000

A double dissociation between the rat hippocampus and medial caudoputamen in processing two forms of knowledge.

Rats with hippocampus, medial caudoputamen (CPU), lateral CPU, or control lesions were trained on declarative and procedural knowledge variants of a novel rodent sequential learning task. Medial CPU lesions impaired rats' ability to learn the procedure of running through a sequence of open maze arms but did not disrupt their capacity to explicitly generate (i.e.. "declare") maze arm sequences. Hippocampus lesions produced the opposite set of results. Rats with lateral CPU lesions were not impaired on either version of the task. Transfer tests indicated that control rats predominantly used egocentric cues to solve the procedural task and allocentric spatial cues to solve the declarative task. These findings suggest a double dissociation between the medial CPU and hippocampus in processing egocentric-procedural and allocentric-declarative sequential information, respectively.

Animals↗
PubMed1982

Some cognitive effects of frontal-lobe lesions in man.

The study of patients undergoing unilateral frontal-lobe excisions for the relief of focal epilepsy has revealed specific cognitive disorders that appear against a background of normal functioning on many intellectual, perceptual and memory tasks. Lesions that invade the frontal eye field cause subtle impairments of voluntary oculomotor control, which reveal themselves as an inability to suppress an initial glance at a potentially distracting stimulus. After frontal lobectomy in either hemisphere, deficits are found quite consistently on motor-differentiation tasks (Konorski 1972) in which the subject must learn to produce different responses to different, randomly presented, environmental signals. More directly related to the concept of planning are those sequential tasks in which the subject is free to choose his own order of responding, but must not make the same response twice. Here the left frontal lobe plays the major role, a finding consistent with the notion of left-hemisphere dominance for the programming of voluntary actions. In contrast, the right frontal lobe appears to be more critically involved in monitoring the temporal sequence of externally ordered events, although the verbal or non-verbal nature of the stimuli remains a relevant factor.

Adult↗
PubMedDate not supplied

Learning of sensory sequences in cerebellar patients.

A possible role of the cerebellum in detecting and recognizing event sequences has been proposed. The present study sought to determine whether patients with cerebellar lesions are impaired in the acquisition and discrimination of sequences of sensory stimuli of different modalities. A group of 26 cerebellar patients and 26 controls matched for age, sex, handedness, musicality, and level of education were tested. Auditory and visual sensory sequences were presented out of different sensory pattern categories (tones with different acoustic frequencies and durations, visual stimuli with different spatial locations and colors, sequential vision of irregular shapes) and different ranges of inter-cue time intervals (fast and slow). Motor requirements were small, with vocal responses and no time restrictions. Perception of visual and acoustic stimuli was generally preserved in patients and controls. The number of errors was significantly higher in the faster tempo of sequence presentation in learning of sequences of tones of different frequencies and in learning of sequences of visual stimuli of different spatial locations and different colors. No difference in tempo between the groups was shown. The total number of errors between the two groups was identical in the sequence conditions. No major disturbances in acquisition or discrimination of various sensory sequences were observed in the group of cerebellar patients. Sequence learning may be impaired only in tasks with significant motor demands.

Acoustic Stimulation↗
PubMedDate not supplied

Extinction and renewal of Pavlovian modulation in human sequential Feature Positive discrimination learning.

Using a conditioned suppression task, we investigated extinction and renewal of Pavlovian modulation in human sequential Feature Positive (FP) discrimination learning. In Experiment 1, in context a participants were first trained on two FP discriminations, X-->A+/A- and Y-->B+/B-. Extinction treatment was administered in the acquisition context a (aaa group) or in a new context b (aba group), and comprised X-->A- extinction and Y- control trials. Discriminative X-->A/A responding was lost in both groups when tested in the extinction context, but partially recovered in the aba and not in the aaa group when tested in the acquisition context, suggesting extinction and renewal of extinguished modulation. The same was observed for the Y-->B/B control pair, however, questioning whether the loss of discriminative X-->A/A responding represented genuine extinction of modulation. In Experiment 2, including only aba groups, participants were trained in context a on two FP discriminations, X-->A+/A- and Y-->B+/B-, after which the group "Extinction" was exposed to X-->A- extinction trials in context b, whereas the group "Control" was exposed to X- control trials; concurrently, both groups received further Y-->B+/B- training. In the group Control, differential Y-->B/B and X-->A/A responding were acquired and maintained throughout the experiment. In the group Extinction, while Y-->B/B responding was also maintained throughout, differential X-->A/A responding disappeared because of X-->A- extinction treatment when tested in the extinction context b, but partially reappeared when tested in the acquisition context a. This evidences aba-renewal of extinguished modulation.

Adolescent↗
PubMed1999

Reversing the phonological similarity effect.

The phonological similarity effect--poor retention of order for lists of similar-sounding items--is a benchmark finding in the short-term memory literature. In our first two experiments, we show that the effect actually reverses following relatively brief periods of distraction, yielding better order retention for similar than for dissimilar lists, provided that different items are used on every trial. In Experiment 3, the same items were used on every trial and similar lists produced poorer performance across all three retention intervals. The results are interpreted from a general discrimination framework: Items are viewed as occupying positions in a multidimensional space defined by list and within-list dimensions.

Adult↗