Effects Of Frontal Lesions Research Articles

The Doors and People Test: The effect of frontal lobe lesions on recall and recognition memory performance.

Objective: Memory deficits in patients with frontal lobe lesions are most apparent on free recall tasks that require the selection, initiation, and implementation of retrieval strategies. The effect of frontal lesions on recognition memory performance is less clear with some studies reporting recognition memory impairments but others not. The majority of these studies do not directly compare recall and recognition within the same group of frontal patients, assessing only recall or recognition memory performance. Other studies that do compare recall and recognition in the same frontal group do not consider recall or recognition tests that are comparable for difficulty. Recognition memory impairments may not be reported because recognition memory tasks are less demanding. Method: This study aimed to investigate recall and recognition impairments in the same group of 47 frontal patients and 78 healthy controls. The Doors and People Test was administered as a neuropsychological test of memory as it assesses both verbal and visual recall and recognition using subtests that are matched for difficulty. Results: Significant verbal and visual recall and recognition impairments were found in the frontal patients. Conclusion: These results demonstrate that when frontal patients are assessed on recall and recognition memory tests of comparable difficulty, memory impairments are found on both types of episodic memory test.

The neonatal rat as a developmental animal model of attention deficit hyperactivity disorder: Effects of frontal lesions on activity and learning.

We examined a developmental animal model of Attention Deficit Hyperactivity Disorder (ADHD) by evaluating the effects of suppressed frontal cortical functioning on habituation in neonatal rats. Frontal cortical activity was suppressed with brain transections in neonatal rats 3, 6, 9, or 12 days of age. Pups were tested in a habituation-to-odor paradigm and behaviors (general activity, headwaving, probing, and rolling) were recorded. Frontal cortical suppression via brain transection resulted in significantly higher activity levels in 3-day-old rats, particularly with regard to rolling, suggesting that the frontal cortex is involved in the regulation of this age-dependent behavior. Frontal transections also increased probing during the odor habituation test in 12-day-old pups. Results are consistent with the neuropsychological research regarding frontal cortical functioning and inhibition in children with ADHD, and suggest that neonatal rats with frontal lesions may provide a useful developmental animal model for studying ADHD.

THE PREFRONTAL CORTEXEXECUTIVE AND COGNITIVE FUNCTIONS.

Edited by A. C. Roberts, T. W. Robbins and L. Weiskrantz . 1998. Pp. 248. Oxford: Oxford University Press. Price £22.99. ISBN 0-19-852441-2. The function of the prefrontal cortex is as fascinating as it is elusive. Whilst damage to more posterior regions produces fairly blatant deficits of function, the effect of frontal brain lesions has proved far more difficult to characterize, although no less devastating to the lives of patients. Early reports told of individuals with no apparent loss of intellectual function, yet whose behaviour changed so drastically that they were never able to resume the lives that they had led before. Part of the problem has undoubtedly been that the cognitive processes underlying abilities which are impaired by prefrontal damage, such as planning, reasoning and problem solving, have not been well understood. A strong theoretical framework within which to interpret the effects of frontal lesions has therefore been lacking. This situation has now changed considerably and the chapters in The Prefrontal Cortex—Executive and Cognitive Functions reflect the ever-increasing degree of theoretical, and technical, sophistication that has been brought to bear on this area of study. The book consists of 15 chapters based on contributions to a discussion meeting of the Royal Society of London. As one would expect from a meeting of this calibre, the contributions are from some of the most prominent researchers in the field. An introduction by A. C. Roberts …

Neuropsychology of mental programming: an approach for the evaluation of frontal lobe dysfunction

Patients with frontal lobe lesions tend to have poor psychosocial recovery, yet they may perform well on common cognitive tests. Their habitual cognitive skills seem to be preserved, whereas the purposeful utilization of skills in novel situations is impaired. This paper reviews neuropsychological disorders and models of mental programming. An approach for the evaluation of programming deficits is presented and some implications of the conception are considered. Programming is defined as the subjective optimization of subgoals for the achievement of the overall goal with available skills. It is posited that programming is critically dependent on prefrontal functions. Measures of programming were found to be sensitive to the effects of frontal lesions and closed-head injuries, as well as, to predict subsequent social recovery. Programming can be seen as an intermediate process between performance and motivation, the subjective optimization of subgoals integrates motivation and skills (operational resources) to purposeful activity.

Effects of frontal lesions on a selective attention task

We set out to test the hypothesis that patients with frontal damage are specifically disabled in carrying out tasks requiring a high level of controlled attention. A group of patients with frontal lesions and another group of patients with retrorolandic lesions were tested for selective attention on a computerized task designed to produce a conflict situation between automatic and controlled processes. Frontal patients proved to be significantly more prone to errors of commission (false alarms) than retrorolandic patients.

The effects of frontal lesions on brain hypersynchronous bursting and behavioral activity

Photically evoked after-discharge (PhAD) bursting was examined in lightly restrained albino rats following frontal and mid-cortical lesions. The initial effect of dorsal frontal lesions was to significantly suppress PhAD occurrence. Spontaneous activity as measured on an open-field arena was examined as a second variable. Frontally lesioned animals were significantly more active than mid-cortically lesioned and non-lesioned control animals in the initial stages of behavioral testing. These results indicate that the frontal cortex has an inhibitory influence on reticular formation (rf) arousal mechanisms which are responsible for behavioral arousal and the modulation of hypersynchronous burst-like phenomena occurring at the level of the cortex.

Cortical stimulation and suppression of activity in the rat

Low-frequency electrical stimulation at sites in the frontal cortex of the rat will suppress running in an activity wheel, but will have no effect on general activity measured in a stabilimeter. This confirms a prediction made from the effects of frontal lesions on these two kinds of activity. No evidence of abnormality in the EEG was observed following frontal stimulation. Stimulation in the frontal cortex probably influences the same inhibitory processes that are modified by frontal lesions. Further results indicate that the differential effects of frontal stimulation on running and general activity may be partly due to differences in response effort required.

An experimental investigation of Luria's theory on the effects of frontal lobe lesions in man

Tasks on which Luria has predicted patients with lesions of the frontal lobes would be impaired were given to 48 patients with unilateral localised lesions. Deficits were found, although the nature of impairments and their relationship to specific locus of lesion were not as predicted. In patients with frontal lobe damage, relatively unimpaired verbal responses were found in association with defective motor responses on one task only. The inability to utilise overt verbalisation to regulate motor performance was likewise found to be not as general as Luria has hypothesised. The deficits are discussed in relation to known effects of frontal lesions in man and non-human primates.

Frontal lesions impair habituation of the head-shake response in rats

The effect of frontal lesions on habituation of the head-shake response was investigated. Two groups of eight male albino rats were given two sessions of 40 stimulated trials each, 24 hr apart. Each session was followed by a retention test at 30 min. The stimulus was a mild puff of air directed at the pinna of the ear. A marked decrement in response frequency occurred from the first to the last trial block, and was highly significant, as determined by nonparametric analyses. One group of rats was then lesioned in the frontal cortex, bilaterally. The other group was sham-operated. The habituation procedure was repeated after 7 days recovery from surgery. The sham-operated control group behaved as before. Frontal rats, however, showed impaired rate of habituation and a much higher terminal level of responding, compared to control rats. These results were highly significant. In addition, the frontal rats did not retain habituation at 30 min, in contrast to control rats. Control rats did not recover above 50 per cent of their initial level of responding. Four more rats were cingulectomized and compared with four control rats. The cingulectomized rats performed no differently from controls, on either major sessions or retention tests.

Effects of frontal lesions on “go-no go” avoidance behaviour in normal and scopolamine-treated rats☆

Abstract Rats were trained in a shuttle-box to give active avoidance responses to a light signal, and passive avoidance responses to a buzzer-light stimulus complex (“go-no go” discrimination with symmetrical punishment). Localized dorsal frontal lesions provoked a marked fall in performance, consisting mainly of a disruption of passive avoidance in non-overtrained animals. Both active and passive avoidance deficits were observed in rats overtrained before operation, although the overall disruption (as measured by total errors) was about the same in non-overtrained and overtrained operates. Postoperative relearning took place with little or no saving. In another experiment animals were subjected to frontal lesions after repeated treatment with scopolamine until they were able to perform at criterion level in spite of drug administration. After postoperative relearning these animals were shown to have re-acquired a marked sensitivity to the drug. The data obtained in appropriate controls indicated that surgical procedures, postoperative interruption of testing and discontinuation of treatment were responsible for only a small part of the resensitization.

Some paradoxical effects of bilateral lesions in the frontal cortex in rats

Rats with bilateral lesions of the frontal cortex were trained to discriminate between patterns of horizontal and vertical black and white stripes. The preference established on the initial discrimination learning was then reversed a total of eight times, e.g. if vertical stripes were positive on Reversal R 0, horizontal stripes were positive on Reversal R 1, vertical stripes on Reversal R 2, and so on. On the initial discrimination and each of the eight successive reversals, the frontal animals required fewer trials to reach criterion than a mock operated control group. Detailed analyses of the results enabled a comparison to be made between several possible competing explanations of the observed differences. It is concluded that the explanation which best fits the present results and those of other relevant studies is that the effect of frontal lesions is to reduce the anxiety and frustration which are otherwise generated by a task in which every time the animal reaches criterion with one set of stimuli, the signs of the stimuli are immediately reversed.

Effect of frontal lesions on performance of sequential tasks by monkeys

Sequential behavior was studied in monkeys with frontal and inferotemporal lesions. An automated discrimination apparatus was used for training. Postoperative retention was assessed in two types of test; one, which required the subject to so order his response that without repetitions he had to push all of several cued panels (internally ordered sequence test) and another, in which the exact order of pushing a series of panels was determined by cues displayed on the panels (externally ordered sequence test). In some animals original learning of this last test was studied postoperatively. The prediction was that the monkeys with frontal lesions would fail internally ordered sequence task but would be able to follow a sequence where external cues can guide the behavior sequence. Those with inferotemporal lesions would show a deficit in the latter test due to their known handicap in visual discrimination problems. The results obtained on those with frontal lesions on the non-cued task confirmed our hypothesis. The subjects with inferotemporal lesions showed no deficit on this task. On the cued task, monkeys with frontal lesions had good postoperative retention; the other group varied a great deal on their performance. The pattern of errors of subjects with frontal lesions on the internally ordered sequence revealed a failure in the completion of a task rather than a tendency towards perseveration. Interpretation of the results in those with frontal lesions, suggests a lack of internal representation in order to anticipate the next step of a sequence; this is not compatible with a simple explanation in terms of a defective recent memory.

The effect of frontal lesions in monkeys upon widely-spaced delayed-response trials.

The effect of frontal lesions in monkeys upon widely-spaced delayed-response trials.

A further experimental analysis of the behavioral deficit that follows injury to the primate frontal cortex

The results of seven experiments that use monkeys are reported. Behavior is examined in modifications of the Yerkes or Wisconsin General Testing Apparatus and in operant conditioning situations. The focus of the studies is the effect on behavior of removal of the frontal eugranular isocortex; unoperated controls and controls with the inferotemporal cortex removed serve as background to the studies. The first two experiments test whether the effects of frontal lesions are restricted to the visual or the somatic sensory mode. The results show that they are not. The next two experiments test whether the effects of the lesion are similar to changes in behavior produced by starvation. Again the results show that there is no similarity. However, the experiment that follows reveals an intersting finding: Monkeys with frontal lesions do not react as do the controls when the test apparatus runs out (deliberately) of rewards. The final pair of experiments explore further the conditions over which this altered behavior can be demonstrated. The results of these experiments show that when the situation is made ambiguous in one manner—i.e., by increasing the number of alternatives of choice—the frontal injury has no effect. On the other hand, the lesions do modify behavior when the ambiguity of the situation is increased by making the relationships between stimuli (cueing or reinforcing) and response variable, i.e., unreliable.