Supplementary cues and delayed-alternation performance of frontal monkeys.

Tested 4 female and 3 male rhesus monkeys that had sustained total or partial ablation of dorsolateral frontal cortex in the Wisconsin General Test Apparatus under variations of the delayed-alternation (DA) task involving supplementary articular-somesthetic or kinesthetic cues. DA performance improved when supplementary articular-somesthetic cues were introduced. Ss with ablation of sulcus principalis demonstrated improvement on DA when supplementary kinesthetic cues were provided; Ss with total dorsolateral ablation did not. Findings support the concept of prefrontal cortex as a gnostic area of the kinesthetic analyzer. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of one-stage and serial ablations of the middle third of sulcus principalis on delayed alternation performance in monkeys.

Investigated recovery of a spatial delayed alternation habit following partial frontal lesions in 9 mature rhesus monkeys. All Ss subjected to serial ablation of the middle third of sulcus principalis were found to be capable of reacquiring preoperative levels of performance on the task. However, 1-stage removal of the mid-principalis region resulted in both more severe and more protracted impairments than were evident after serial surgery. Results in conjunction with previous findings suggest that recovery following serially induced neurological insult may be dependent upon the integrity of neural tissue adjacent to the locus of injury. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of the contributions of the frontal and parietal association cortex to spatial localization in rats.

Compared 15 rats with lesions of the medial frontal, orbital frontal, or parietal cortex with 5 rats with complete removal of the neocortex and 5 normal controls on 3 spatial tasks: Morris water task, radial arm maze, and spatial reversals in a Grice box. Decortication produced severe impairments in the acquisition of all 3 tasks. Ss with parietal cortex lesions were relatively unimpaired at any of the tasks, although they had a significant deficit on the spatial reversal task and had a short-term memory impairment on the radial arm maze. In contrast, Ss with medial frontal lesions had a significant, but relatively mild, impairment on the radial arm maze and were poor at learning the water task. Ss with orbital frontal lesions were nearly as impaired on the radial arm maze and water task as decorticate Ss. Results suggest that the frontal and parietal cortex of rats play different roles in the control of spatial orientation but do not support the view that egocentric and allocentric spatial orientation are related to frontal and parietal mechanisms, respectively. In addition, results suggest that the frontal cortex plays a larger role in the control of spatially guided behavior than has been previously recognized and that both the medial frontal and the orbital frontal cortex play a dissociable role in the control of spatial orientation. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lateralized anterior and posterior lesions and performance on Digit Span and Russell's revision of the Wechsler Memory Scale.

Performance on the Russell (1975) revision of the Wechsler Memory Scale and the Digit Span subtest of the Wechsler Adult Intelligence Scale (WAIS) by Ss with lateralized anterior and posterior lesions was investigated. Ss were right-handed men whose brain lesions were identified on the basis of neurodiagnostic tests as being lateralized to either the left or right hemisphere and restricted to either the anterior or posterior side of the central sulcus. A normal comparison group was formed of Ss suspected of having neurological damage and referred for neuropsychological testing but who had normal neurodiagnostic examinations. It was predicted that both the laterality and caudality of lesions would affect memory task performance. This prediction was fully supported for the logical memory task and partially supported for the figural memory and digit span tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neonatal frontal lesions in the rat: Sparing of learned but not species-typical behavior in the presence of reduced brain weight and cortical thickness.

Used 70 Long-Evans rats to compare Ss that underwent complete removal of the cortex anterior to bregma in adulthood (frontal cortex) with Ss who had similar removals at 7 or 25 days of age. Excision of the frontal cortex in adult Ss produced transient aphagia, chronic motor abnormalities in feeding, a chronic drop in body weight, increased activity in running wheels, impaired performance on a spatial reversal learning task, and chronic abnormalities in a variety of species-typical behaviors. Lesions in infants failed to produce aphagia, a chronic drop in body weight, increased activity, or impaired learning of a spatial reversal task. However, infant lesions did not allow sparing of complex species-typical behaviors. In comparison with controls and Ss operated on in adulthood, cerebral hemispheres of neonatal operates were smaller both in surface dimensions and weight, the thalamus was smaller, and the cerebral cortex was thinner. Data imply that there may be substantially less sparing of function following frontal cortex lesions in infancy than previously believed and that neonatal frontal lesions in rats have significant effects on brain development in regions far removed from the actual site of surgical excision. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial memory deficits in patients with lesions to the right hippocampus and to the right parahippocampal cortex

Spatial memory tasks, performance of which is known to be sensitive to hippocampal lesions in the rat, or to medial temporal lesions in the human, were administered in order to investigate the effects of selective damage to medial temporal lobe structures of the human brain. The patients had undergone thermo-coagulation with a single electrode along the amygdalo-hippocampal axis in an attempt to alleviate their epilepsy. With this surgical technique, lesions to single medial temporal lobe structures can be carried out. The locations of the lesions were assessed by means of digital high-resolution magnetic resonance imaging and software allowing a 3-D reconstruction of the brain. A break in the collateral sulcus, dividing it into the anterior collateral sulcus and the posterior collateral sulcus is reported. This division may correspond to the end of the entorhinal/perirhinal cortex and the start of the parahippocampal cortex. The results confirmed the role of the right hippocampus in visuo-spatial memory tasks (object location, Rey-Osterrieth Figure with and without delay) and the left for verbal memory tasks (Rey Auditory Verbal Learning Task with delay). However, patients with lesions either to the right or to the left hippocampus were unimpaired on several memory tasks, including a spatial one, with a 30 min delay, designed to be analogous to the Morris water maze. Patients with lesions to the right parahippocampal cortex were impaired on this task with a 30 min delay, suggesting that the parahippocampal cortex itself may play an important role in spatial memory.     

Spatial mapping, working memory, and the fimbria–fornix system.

13 Long-Evans male hooded rats with lesions severing either the subcallosal fornix (Fo) or the medial half of the fimbria (Fi) were compared with 9 control (Co) and sham-operated Ss in a working memory task (serial alternation) and a reference memory task (cue-guided alternation). Neither task required spatial mapping strategy. Findings indicate that damaging the Fi, but not the Fo, caused a severe deficit in the serial alternation task. Analysis of individual performance revealed that Fi Ss either adopted a "side strategy," resulting in chance performance, or actively repeated previous successful choices, resulting in worse than chance performance. This active perseveration required an intact working-memory mechanism. In the cue-guided alternation task, Fo Ss proved superior to Co and Fi Ss. Findings are inconsistent with notions that the exclusive role of the hippocampus is spatial mapping or storing of recent memories, and indicate differential involvement of the fimbria and fornix fibers in behavior. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neonatal frontal lesions in hamsters impair species-typical behaviors and reduce brain weight and neocortical thickness.

23 Syrian golden hamsters in which the medial or ventral subfields of the frontal cortex were removed at 2 days of age were compared behaviorally and neuroanatomically with 34 Ss experiencing similar lesions at 100 days of age. An additional 18 Ss served as controls. Ss with neonatal lesions showed little sparing of species-typical behaviors such as hoarding and nest building. Although as juveniles the operated Ss did not differ from their littermate controls, as they developed they failed to improve their performance as their littermates did. Nonetheless, under certain environmental conditions, the lesioned Ss were capable of performing the behaviors nearly as proficiently as controls. Compared with Ss operated on in adulthood, the brains of neonatal operates weighed less and the remaining neocortex was thinner. Findings are discussed in terms of functional subregions of the brain, environmental constraint on sparing, and the measurement of behavioral deficits. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intensity difference thresholds in pigeons after lesions of the tectofugal and thalamofugal visual pathways.

Obtained visual intensity difference thresholds from 11 White Carneaux pigeons before and after thalamic lesions. Ss with lesions in nucleus rotundus (the thalamic component of the tectofugal pathway) showed moderate postoperative threshold elevations. After extensive retraining the thresholds returned to the preoperative value. Ss with lesions in the nucleus opticus principalis thalami (OPT), the thalamic component of the thalamofugal pathway, had smaller postoperative threshold elevations than the nucleus rotundus cases, but the deficit did not diminish after extensive retraining. Ss with combined lesions of both pathways (OPT + rotundus) had severe postoperative threshold elevations, which declined with retraining to the level of the Ss with OPT lesions, but not to the preoperative level. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serotonin, the superior colliculus, and grooming behavior in cats with neocortical lesions.

Previous studies of cats with pontile lesions indicate that a serotonergic deficit exists in the superior colliculi and that this deficit is involved in an abnormal grooming behavior. Cats with frontal neocortical lesions exhibit the same serotonergic deficit and abnormal grooming behavior. The present study with 20 male cats established that the serotonergic deficit is involved in mediation of the abnormal grooming behavior in cats with frontal neocortical lesions. Microinjections of 5-hydroxytryptophan (5-HTP) and 5-hydroxytryptamine (5-HT) into the superior colliculi abolished or significantly reduced the abnormal behavior in Ss with frontal neocortical lesions, whereas no effects of 5-HTP were observed after injections into the superior colliculi, into the tegmentum beneath the superior colliculi, or into the medial dorsal nucleus rostral to the superior colliculi. Tryptophan, noradrenaline, and gamma-aminobutyric acid had no effect on abnormal behavior when injected into the superior colliculi. Evidence implicating a serotonergic deficit in the mediation of abnormal behavior was obtained by systemic injections: The behavior was abolished with 5-HTP in Ss with frontal neocortical lesions and in adrenalectomized Ss previously treated with para-chlorophenylalanine. Findings also demonstrate that the abnormal behavior is induced by frontal neocortical lesions and not by more caudal lesions of the cortex. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for involvement of orbitofrontal cortex in memory functions: An interference effect.

Although it is frequently stated that the frontal lobes play a significant role in memory function, research proof has been ambiguous at best. The present study investigated this problem by administering a variety of memory tests (e.g., Wechsler Memory Scale, WAIS) to 16 schizophrenic patients who had undergone prefrontal leukotomy approximately 25 yrs earlier. Ss were divided into 3 groups on the basis of recovery after surgery. Two comparison groups (5 psychiatric and 5 normal controls) were established to control for psychiatric symptomatology, years of institutionalization, age, and years of education. Results indicate that large bilateral orbitofrontal lesions may not result in amnesia; in fact, the nonoperated schizophrenic control group performed the most poorly. Proactive interference was demonstrated, however, resulting in significant impairment for all Ss with prefrontal lobe damage despite normal scores on commonly used memory tests. Ability to maintain consistent and directed attention and to overcome interference is proposed as a role of the frontal lobes in memory function. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retrospective and prospective coding of information: Dissociation of parietal cortex and hippocampal formation.

Animals with sham operations, hippocampal formation, or small and large parietal cortex lesions were trained in a task that required memory for short or long lists of items (spatial locations). Sham-operated Ss showed an increase in errors as a function of set size (2–8 items) followed by a decrease in errors with a set size of 10 items, suggesting the use of both retrospective and prospective memory codes. Ss with hippocampal formation lesions made errors for all set sizes, reflecting an inability to use a retrospective and prospective memory code. Failure to use a prospective code is probably a function of the inability to use a retrosepctive code (i.e., the S needs to remember first what has occurred before it can determine what information lies ahead). Ss with small or large parietal cortex lesions made most of their errors for the longest list length, reflecting an inability to shift from a retrospective to prospective memory code. The hippocampal formation might mediate new incoming information (data-based memory processing) and thus accentuate the importance of a retrospective memory code. The parietal cortex might mediate existing knowledge (expectancy-based memory processing) and thus facilitate the utilization of a prospective memory code. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual experience, unilateral cortical lesions, and lateralization of function in rats.

Measured the effects of early visual experience and later unilateral neocortical lesions on the behavior of 30 male hooded Long-Evans rats in an open-field, 17-arm spatial maze and on a visual field or perimetry test. 30 Ss were formed into 6 groups—3 light-reared (LR) and 3 dark-reared (DR)—of 5 Ss each in order to receive right-, left-hemisphere, or sham neocortical lesions. The comparison of behavior observed in the open field revealed that LR Ss with right-hemispheric lesions were more active and reared more than any of the other Ss. On the radial-maze task, in which 8 of 17 arms were baited, all Ss with lesions performed less effectively than did sham-operated Ss. The effect of the lesions was significantly greater for LR than for DR Ss. Perimetry testing revealed that, although the lesioned Ss did react to stimuli throughout their visual field, some contralateral neglect was evident in both LR and DR Ss; the lesions had a greater impact on orientation behavior of LR Ss, however. No evidence emerged of any functional asymmetry following the unilateral cortical lesions. Findings are discussed in terms of V. H. Denenberg's (1981) hypothesis about cerebral and functional asymmetry in the rat. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory for spatial information in young and old adults.

Evaluated the claim that memory for spatial information is automatic. 46 18–35 yr olds and 49 51–80 yr olds studied a map containing 12 structures. Half the Ss in each age group were asked to remember both the structures and their locations (intentional learning), and the remaining half were led to believe they would be tested only on the structures (incidental learning). Both age and test expectations affected memory for the locations of structures, with older Ss and Ss in the incidental groups performing more poorly. It is concluded that memory for spatial location is not automatic. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pilocarpine and physostigmine attenuate spatial memory impairments produced by lesions of the nucleus basalis magnocellularis.

Three experiments, with 63 male Long-Evans rats, investigated the effects of bilateral ibotenic acid-induced lesions of the nucleus basalis magnocellularis (NBM) on the acquisition and retention of several spatial memory tasks. Maintenance of spatial memory in a food-search task was impaired following NBM lesions. Acquisition of spontaneous alternation and reinforced alternation in a T-maze, but not the acquisition of a position habit, was also significantly impaired in Ss with these lesions. In several of the tasks, there was evidence of some learning in the lesioned Ss after substantial training, although they were significantly deficient when compared with controls. Intraperitoneal administration of the cholinergic agonists physostigmine sulfate (0.5 mg/kg) or pilocarpine nitrate (3 mg/kg) prior to behavioral testing resulted in a rapid and significant improvement in the performance of the lesioned Ss. Lesions significantly reduced the activity of choline acetyltransferase in the anterior and the posterior neocortex but not the hippocampus. Results indicate that the cholinergic projections originating in the NBM are involved in the learning and memory of spatial tasks. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of prefrontal cortex ablation in neonatal, juvenile, and young adult rats.

Long-Evans hooded rats sustaining lesions in the medial (MF) or the orbital (OF) prefrontal cortex at various ages (10, 25, 40, or 60 days postnatally) were tested as adults on a series of behavioral tasks that are known to be sensitive to such lesions in adults. On spatial alternation learning, both the 40- and 60-day MF Ss were seriously impaired, whereas neither the 10- nor the 25-day MF Ss differed from controls. On a hoarding task, 25- and 60-day MF Ss hoarded less food than either controls or 10-day MF Ss. Lesions of OF cortex in males at 40 or 60 days significantly increased running-wheel activity; OF lesions in both sexes at 25 days of age or later decreased the rate of continuous reinforcement reacquisition relative to controls, whereas 10-day OF Ss did not differ from controls on either task. Thus, Ss with lesions of either frontal area at 10 days of age showed complete behavioral sparing on all measures. The effects of lesions at later ages varied with the behavioral task employed and with lesion locus. Although the 10-day Ss received a somewhat longer postoperative recovery interval than most of the later operates, these results cannot be explained on the basis of recovery time alone. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal and spatial context memory in patients with focal frontal, temporal lobe, and diencephalic lesions

Patients with focal frontal, temporal lobe, or diencephalic lesions were investigated on measures of temporal (recency) and spatial (position) context memory, after manipulating exposure times to match recognition memory for targets (pictorial stimuli) as closely as possible. Patients with diencephalic lesions from an alcoholic Korsakoff syndrome showed significant impairment on the temporal context (recency) task, as did patients with frontal lesions penetrating the dorsolateral frontal cortex, according to MRI (and PET) evidence. Patients with temporal lobe lesions showed only a moderate (non-significant) impairment on this task, and patients with medial frontal lesions, or large frontal lesions not penetrating the dorsolateral cortical margins, performed as well as healthy controls at this task. On the spatial context memory task, patients with lesions in the temporal lobes showed significant impairment, and patients with right temporal lesions performed significantly worse than patients with left temporal lesions. Patients with diencephalic lesions showed only a modest (non-significant) impairment on this task, and the frontal lobe group performed normally. When a group of patients with temporal lobe lesions resulting from herpes encephalitis were examined separately, an identical pattern of results was obtained, the herpes group being significantly impaired on spatial memory and showing a trend towards impairment for temporal context memory. There were strong correlations between anterograde memory quotients and context memory performance (despite the use of an exposure time titration procedure) and a weak association in the frontal group with one frontal/executive task [corrected] (card-sorting perservations). It is predicted that correlations between temporal context memory and frontal/executive tasks will be greater in samples of patients all of whom have frontal lesions invading the dorsolateral cortical margin.     

Grooming reflexes and Brown-Séquard epilepsy in cats with pontile lesions.

The literature on the relation between the scratch reflex and Brown-Séquard epilepsy in the guinea pig indicates that the scratch reflex is a stimulus-induced myoclonus that is the 1st component of a complete seizure. In the present experiment, with 26 male cats, Ss with pontile or frontal neocortical lesions exhibited the scratch reflex and other grooming reflexes. The grooming reflexes in Ss with pontile lesions developed over a period of a year or more into complete seizures that were similar to Brown-Séquard epilepsy. Cinematographic analyses revealed that the scratch reflex in Ss with pontile or frontal neocortical lesions had the same frequency and the same complex spatial and temporal pattern as normal scratching behavior. The myoclonus of the complete seizures was identified as the scratch reflex, representing a vigorous and long-lasting afterdischarge. Reconstructions of the pontile lesions indicated that the lateral and rostral portions of the paralemniscal tegmental fields were destroyed along with portions of the pontile gray and pyramidal tract. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial septal lesions in rats produce permanent deficits for strategy selection in a spatial memory task.

Rats with medial septal (MS) lesions have been shown to consistently use a stereotypic response strategy rather than a nonstereotypic spatial learning strategy when solving a radial maze task. The present study examined the long-term effects of MS lesions on spatial memory performance to determine whether MS lesions permanently impair rats from using a nonstereotypic strategy. Male rats, initially trained on a radial maze, were given either MS or sham surgeries and were subsequently retested on the maze. Consistent with previous studies, all Ss with MS lesions used a stereotypic strategy during the postoperative retest. However, when placed through a series of retraining phases that required the S to use a nonstereotypic strategy to solve the task, none of the MS Ss could solve the task. These results indicate that lesions of the MS produce permanent spatial memory deficits that cannot be restored through extensive behavioral training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Monkeys with combined amygdalo-hippocampal lesions succeed in object discrimination learning despite 24-hour intertrial intervals.

14 rhesus monkeys, including 3 who had undergone amygdalo-hippocampal lesions before participating in a previous visual learning study, were trained on object-discrimination trials that were separated by 24 hrs to test the hypothesis that the 24-hr interval would prevent Ss with limbic lesions from learning. It is noted in previous research that monkeys with combined amygdalo-hippocampal removal show severe impairments on visual-memory tasks after delays of 1–2 min, yet they learn visual-discrimination habits nearly as quickly as normal monkeys with intertrial intervals of the same duration. Results of the present study indicate that, as long as the lesions did not encroach on the inferior temporal cortex, operated Ss could acquire concurrent sets of 20 object-discrimination habits at the same rate as unoperated Ss in an average of approximately 10 trials/set. Findings suggest that learning and retention processes are divisible into a mechanism for memory formation that is dependent on the limbic system and a mechanism for habit formation that is not. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)