Age-related deficits in generation and manipulation of mental images: I. The role of sensorimotor speed and working memory.

The authors investigated age-related slowing of information processing in mental imagery tasks. Eighty-five healthy adults (ages 18 to 77) performed a visual, sensorimotor, reaction-time task; a visual-perceptual choice reaction task; and 3 mental imagery tasks that varied in apparent difficulty and involved stimuli at 2 levels of graphic complexity. Age was associated with prolongation of response time across all tasks and both levels of stimulus complexity. Accuracy of response was adversely affected by increase in stimulus complexity in all tasks, whereas it was negatively related to age only on the tasks with substantial mental imagery requirements. Slowing of information processing and reduction in accuracy were mediated by declines in working memory but not by decrease of sensorimotor speed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Age-related deficits in generation and manipulation of mental images: I. The role of sensorimotor speed and working memory": Correction to Briggs et al. (1999).

Reports several errors in the original article by S. Briggs, N. Raz and W. Marks (Psychology & Aging, 1999 (Sep.), Vol.14(3), 427–435). None of the errors alter the conclusions of the article. (The following abstract of this article originally appeared in record 1999-11243-006). The authors investigated age-related slowing of information processing in mental imagery tasks. Eighty-five healthy adults (ages 18 to 77) performed a visual, sensorimotor, reaction-time task; a visual-perceptual choice reaction task; and 3 mental imagery tasks that varied in apparent difficulty and involved stimuli at 2 levels of graphic complexity. Age was associated with prolongation of response time across all tasks and both levels of stimulus complexity. Accuracy of response was adversely affected by increase in stimulus complexity in all tasks, whereas it was negatively related to age only on the tasks with substantial mental imagery requirements. Slowing of information processing and reduction in accuracy were mediated by declines in working memory but not by decrease of sensorimotor speed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delayed-matching and delayed-response deficit from cooling dorsolateral prefrontal cortex in monkeys.

Tested the hypothesis that the functional integrity of the dorsolateral prefrontal cortex is important for short-term memory of both spatial and nonspatial information. In 3 experiments, a total of 4 adult male rhesus monkeys were tested in delayed matching-to-sample (DMS) and delayed-response (DR) tasks with delays of 0-32 sec under 3 different conditions: frontal cooling (FC), parietal cooling (PC), and normal temperature (noncooling, NC). The proportion of correct responses decreased in NC as a function of the delay. This decrease was significantly accentuated by FC, whereas it was not modified by PC. At each delay, the decrement elicited by FC was as large in DR as in DMS. Reaction time and activity normally increased as a function of delay, and these changes were enhanced by FC. The FC-induced decrements in proportion of correct responses suggest a faster loss from short-term memory of both spatial and nonspatial information. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of prefrontal cortex in predictive fear learning.

Pavlovian fear conditioning depends on prediction error, or the discrepancy between actual and expected outcomes. We used immunohistochemistry, neuronal tract tracing, and reversible inactivation to study the role of prefrontal cortex and thalamocortical pathways in predictive fear learning. Unexpected, but not expected, conditioned stimulus (CS)–unconditioned stimulus (US) presentations caused increased c-Fos expression in the prefrontal cortex (PFC), midline thalamus, lateral amygdala, as well as retrograde labeled midline thalamic afferents to PFC. Reversible inactivation of dorsomedial PFC, but not infralimbic PFC, prevented the associative blocking of fear learning. These results suggest a role for dorsomedial PFC (dmPFC), and a thalamic → dmPFC pathway, in signaling whether or not aversive events are expected or unexpected and so whether they are to be learned about. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rapid-rate transcranial magnetic stimulation of left dorsolateral prefrontal cortex in drug-resistant depression

BACKGROUND: Lesion and neuroimaging studies suggest that left prefrontal lobe dysfunction is pathophysiologically linked to depression. Rapid-rate transcranial magnetic stimulation (rTMS) to prefrontal structures has a lateralised effect on mood in normal volunteers, and several preliminary studies suggest a beneficial effect of rTMS on depression. However, adequately controlled studies have not been conducted. METHODS: We have studied the effects of focal rTMS on the depressive symptoms in 17 patients with medication-resistant depression of psychotic subtype. The study was designed as a multiple cross-over, randomised placebo-controlled trial. Sham rTMS and stimulation of different cortical areas were used as controls. FINDINGS: Left dorsolateral prefrontal cortex rTMS resulted in a significant decrease in scores on the Hamilton depression rating scale HDRS (from 25.2 to 13.8) and the self-rated Beck questionnaire BQ (from 47.9 to 25.7). 11 of the 17 patients showed pronounced improvement that lasted for about 2 weeks after 5 days of daily rTMS sessions. No patient experienced any significant undesirable side-effects. INTERPRETATION: Our findings emphasise the role of the left dorsolateral prefrontal cortex in depression, and suggest that rTMS of the left dorsolateral prefrontal cortex might become a safe, non-convulsive alternative to electroconvulsive treatment in depression.     

Age-related deficits in prospective memory: The influence of task complexity.

Younger and older Ss were asked to perform an action whenever target words occurred during a short-term memory task. The difficulty of this prospective memory task was manipulated by varying the delay preceding the occurrence of a target event and by varying the number of different target events. Age-related performance differences emerged when there were several different target events but not when there was 1 target event presented several times. Age-related performance differences, when they occurred, were associated with poorer retrospective memory for the target events. The results were interpreted in terms of a componential analysis of prospective memory, which assumes both similarities and differences between prospective and retrospective memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the medial prefrontal cortex in the play fighting of rats.

Although decorticated rats are able to engage in play, their play is abnormal in three ways. First, decorticates do not display the normal, age-related shifts in defensive strategies during development. Second, decorticates do not modify their defensive tactics in response to the social identity of their partners. Third, decorticates display a global shift in defensive tactics from more complex to less complex strategies. It has been shown that lesions of the motor cortex (MC) selectively produce the abnormal developmental effects on play, and that lesions of the orbitofrontal cortex (OFC) selectively produce the deficits in behavioral discrimination between social partners. In the current set of experiments, we demonstrate that lesions of the medial prefrontal cortex (mPFC) produce the shift from more complex to less complex defensive tactics, while leaving intact the age-related and partner-related modulation of defensive strategies. Thus, we have evidence for a triple dissociation of function between the MC, the OFC, and the mPFC with respect to social play behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of prefrontal cortex in working memory: examining the contents of consciousness

Working memory enables us to hold in our 'mind's eye' the contents of our conscious awareness, even in the absence of sensory input, by maintaining an active representation of information for a brief period of time. In this review we consider the functional organization of the prefrontal cortex and its role in this cognitive process. First, we present evidence from brain-imaging studies that prefrontal cortex shows sustained activity during the delay period of visual working memory tasks, indicating that this cortex maintains on-line representations of stimuli after they are removed from view. We then present evidence for domain specificity within frontal cortex based on the type of information, with object working memory mediated by more ventral frontal regions and spatial working memory mediated by more dorsal frontal regions. We also propose that a second dimension for domain specificity within prefrontal cortex might exist for object working memory on the basis of the type of representation, with analytic representations maintained preferentially in the left hemisphere and image-based representations maintained preferentially in the right hemisphere. Furthermore, we discuss the possibility that there are prefrontal areas brought into play during the monitoring and manipulation of information in working memory in addition to those engaged during the maintenance of this information. Finally, we consider the relationship of prefrontal areas important for working memory, both to posterior visual processing areas and to prefrontal areas associated with long-term memory.     

Memory for duration: role of hippocampus and medial prefrontal cortex

In this task rats had to learn that a three-dimensional object stimulus (a rectangle) that was visible for 2 s would result in a positive (go) reinforcement for one object (a ball) and no reinforcement (no go) for a different object (a bottle). However, if the rectangle stimulus was visible for 8 s then there would be no reinforcement for the ball (no go), but a reinforcement for the bottle (go). After rats learned this conditional discrimination by responding differentially in terms of latency to approach the object, they received large (dorsal and ventral) lesions of the hippocampus, lesions of the medial prefrontal cortex (anterior cingulate and precentral cortex), lesions of the cortex dorsal to the dorsal hippocampus, or served as sham-operated controls. Following recovery from surgery they were retested. The results indicate that there were major impairments following hippocampal lesions, in contrast to cortical control and medial prefrontal cortex lesions, as indicated by smaller latency differences between positive and negative trials on postsurgery tests. In order to ensure that the deficits observed with hippocampal lesions were not due to a discrimination problem, new rats were trained in an object (gray cylinder) duration discrimination task. In this go/no go procedure, the rats were reinforced for a 2-s exposure (duration) of the gray cylinder, but not a 10-s duration, or vice versa. The results indicate that after hippocampal lesions, there was an initial deficit followed by complete recovery. There were no significant changes for the medial prefrontal, cortical control, or sham-operated animals. It appears that the hippocampus, but not the medial prefrontal cortex, is actively involved in representing in short-term memory temporal attribute information based on the use of markers for the beginning and end of the presence (duration) of a stimulus (object).     

Age-related deficits in associative memory: The influence of impaired strategic retrieval.

In 2 experiments, the authors investigated whether impaired strategic retrieval processes contribute to the age-related deficit in associative memory. To do so, they compared older and younger adults on measures of associative memory that place high demands on retrieval processes (associative identification and recall-to-reject) to measures that place low demands on such processes (associative reinstatement and recall-to-accept). Results showed that older adults were severely impaired on associative identification and recall-to-reject measures; relatively intact on recall-to-accept measures, unless recollection was prominent; and intact on associative reinstatement measures. Together, these findings suggest that impairment in strategic retrieval accounts for older adults' deficits in memory for associative information and that this deficit, above and beyond poor binding of items, leads to and amplifies an impairment in overall recollection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial prefrontal cortex lesions cause deficits in a variable-goal location task but not in object exploration.

The role of the medial prefrontal cortex (PFC) in goal-directed behavior was examined in rats with aspiration lesions. In Experiment 1, PFC lesions resulted in an impaired ability to relearn the location of a behaviorally defined goal arm of a plus-maze after it was moved from an initially fixed position. Lesioned rats also exhibited a significantly greater degree of perseveration compared with control animals. Experiment 2 was an object exploration task in which rats had to respond to a change in the layout of the environment. PFC-lesioned rats performed identically to controls, therefore demonstrating that the deficits observed in Experiment 1 did not result from a deficit in the ability to explore the environment. The results are discussed in terms of several competing, but not mutually exclusive explanations of the role of the PFC in navigation and spatial representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related deficits in reality monitoring of action memories.

The authors describe 3 theoretical accounts of age-related increases in falsely remembering that imagined actions were performed (A. K. Thomas & J. B. Bulevich, 2006). To investigate these accounts and further explore age-related changes in reality monitoring of action memories, the authors used a new paradigm in which actions were (a) imagined only, (b) actually performed, or (c) both imagined and performed. Older adults were more likely than younger adults to misremember the source of imagined-only actions, with older adults more often specifying that the action was imagined and also that it was performed. For both age groups, illusions that the actions were only performed decreased as repetitions of the imagined-only events increased. These patterns suggest that both older and younger adults use qualitative characteristics when making reality-monitoring judgments and that repeated imagination produces richer records of both sensory details and cognitive operations. However, sensory information derived from imagination appears to be more similar to that derived from performance for older adults than for younger adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related deficits in component processes of working memory.

Working memory deficits in normal aging have been well documented, and studies suggest that high memory load plus the presence of distraction negatively impacts successful memory performance to a greater degree in older individuals. However, characterization of the component processes that are impaired by these task manipulations is not clear. In this behavioral study, younger and older subjects were tested with a delayed-recognition and recall task in which the encoding and delay period were both manipulated. During the encoding period, the subjects were presented with either a single letter or multiple letters at their predetermined forward letter span, and the delay period was either uninterrupted or interrupted with a visual distraction. There was an age-related impairment of working memory recognition accuracy only in the combination of high memory load and distraction. These results suggest that when working memory maintenance systems are taxed, faulty recognition processes may underlie cognitive aging deficits in healthy older individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related differences in cognition: The role of distraction control.

The ability to ignore or control the processing of distracting information may underlie many age-related and individual differences in cognitive abilities. Using a large sample of adults aged 18 to 87 years, this article presents data examining the mediating role of distraction control in the relationship between age and higher order cognition. The reading with distraction task (Connelly, Hasher, & Zacks, 1991) has been used as a measure of the access function of distraction control. Results of this study suggest that distraction control, as measured by this paradigm, plays an important role in mediating age-related effects on measures of working memory and matrix reasoning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interpretation of differential deficits: The case of aging and mental arithmetic.

A fundamental issue in research on individual differences is the type of evidence sufficient to justify an inference of selective or distinct deficits in relevant theoretical processes. It is proposed that an important consideration is the extent to which the individual differences in 1 variable are independent of those in another variable. Specifically, the suggestion presented here is that a strong conclusion of selective impairment requires evidence that there is significant group-related variance in 1 variable after the variance in the other relevant variable is controlled. Furthermore, an inference that the groups are equivalent on a particular theoretical process requires evidence that the variable presumed to reflect that process has sufficient unique variance to justify the claim that a distinct process is being assessed. The proposed methods are illustrated with 2 studies comparing adults of different ages in mental arithmetic tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of the role of medial prefrontal cortex dopamine receptors in cocaine-induced locomotor activity.

Medial prefrontal cortex (mPFC) dopamine (DA) modulates the motor-stimulant response to cocaine. The present study examined the specific mPFC DA receptor subtypes that mediate this behavioral response. Intra-mPFC injection of the DA D?-like receptor agonist quinpirole blocked cocaine-induced motor activity, an effect that was prevented by coadministration of the D2 receptor antagonist sulpiride. Intra-mPFC injection of the selective D? receptor agonist PD 168,077 or the selective D? receptor agonist SKF 81297 did not alter the motor-stimulant response to cocaine. Finally, it was found that an intermediate dose of quinpirole, which only attenuated cocaine-induced motor activity, was not altered by SKF 81297 coadministration, suggesting a lack of synergy between mPFC D?, and D? receptors. These results suggest that D? receptor mechanisms in the mPFC are at least partly responsible for mediating the acute motor-stimulant effects of cocaine. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related binding deficits and the content of false memories.

The authors examined effects of age-related binding deficits on feature information in false memories for imagined objects (e.g., lollipop) that were similar in shape to seen objects (e.g., magnifying glass). In Experiment 1, location memory for seen objects was lower in older than younger adults and lower still in old-old than young-old adults. Imagined objects, when falsely called seen, were less likely to be attributed to the location of similar seen objects (i.e., congruent attributions) by old-old than young-old adults. In Experiment 2, for younger adults, displaying seen objects for less time (1 s vs. 4 s) reduced both location memory for seen objects and congruent attributions for false memories. Thus, binding deficits may influence the specific content of false memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related deficits in acquisition of a passive avoidance response.

In Exp. I, 80 male albino rats 10, 15, 20, 30, or 100 days old received a brief inescapable shock contingent upon making a step-off response. Step-off latencies increased for all age groups, but rate of learning was significantly faster in older Ss. Learning appeared to be based primarily upon punishment effects rather than general emotionality, since yoked Ss shocked after being placed directly on the grids did not acquire the avoidance response. Exp. II with 120 Ss employed 3 training conditions with independent groups 12, 15, 18, or 21 days old. The step-off response resulted in shock that was either: (a) escapable; (b) inescapable, 1-sec duration; or (c) inescapable, yoked duration. Younger Ss were again significantly inferior to more mature Ss. Escapable shock improved acquisition at 2 age levels, but the effect appeared to be more related to shock duration than to the response contingency. It is suggested that the requirement of withholding a punished response may represent a category of learning that is especially sensitive to maturational changes. (French summary) (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Revisiting the role of the prefrontal cortex in the pathophysiology of attention-deficit/hyperactivity disorder.

Most neural models for the pathophysiology of attention-deficit/hyperactivity disorder (ADHD) have centered on the prefrontal cortex and its interconnections with the striatum and other subcortical structures. However, research only partially supports these models, and they do not correspond with the development of the prefrontal cortex and its interrelated neurocircuitry. The neural and functional development of the prefrontal cortex more closely parallels recovery from ADHD as indicated by the developmental remission of symptomatology. The authors hypothesize that ADHD is due to noncortical dysfunction that manifests early in ontogeny, remains static throughout the lifetime, and is not associated with the remission of symptomatology. Data supporting this neurodevelopmental model of prefrontal cortex function in ADHD are reviewed. Research and treatment implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of dopamine in maintaining intracranial self-stimulation in the ventral tegmentum, nucleus accumbens, and medial prefrontal cortex.

Male albino Wistar rats were prepared with 2 chronic bipolar electrodes implanted ipsilaterally in the ventral tegmentum and either the nucleus accumbens or the medial prefrontal cortex. Once stable intracranial self-stimulation was elicited from both midbrain and forebrain electrodes, 6-hydroxydopamine lesions were placed into the ascending dopaminergic pathways between the rewarding electrode placements at the level of the lateral hypothalamus. Data suggest that dopamine plays an important role in self-stimulation in the ventral tegmentum and contributes to this behavior in the prefrontal cortex. Findings also show that nondopaminergic systems contribute to the phenomenon of brain-stimulation reward. (French summary) (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)