Affective tasks elicit material-specific memory effects in temporal lobectomy patients

Eighteen patients who had undergone a right (9) or left (9) temporal lobectomy (RTL, LTL) including removal of the amygdala and hippocampus were evaluated. Sixteen male and sixteen female undergraduate subjects were evaluated for normative comparison. All subjects were administered Verbal (words) and Visual (faces) paired associates tasks. The present study sought to evaluate material-specific memory after temporal lobectomy, and to compare affective versus neutral memory as well. Thus, there were 4 tasks: Verbal Affective, Verbal Neutral, Visual Affective, and Visual Neutral. The material-specific effects of better Verbal memory performance by the RTL subjects compared to the LTL subjects and better Visual memory performance by the LTL subjects than the RTL subjects were only significant for the Affective tasks, and not the Neutral tasks. Perhaps adding an affective dimension to the material-specific memory tasks engaged the amygdala in addition to the other structures known to be important in memory. A strong interpretaion of the present data is made difficult by task differences and the low average IQ and possible reorganization of function that may have occurred in the patient sample.     

Perception and Priming of Affective Faces in Temporal Lobectomy Patients

Eighteen patients who had undergone standard anterior temporal lobectomy including removal of the amygdala and hippocampus (9 left, LTL; 9 right, RTL) were administered an Affective Task composed of faces depicting negative emotions, and a Neutral Task consisting of faces with different lighting and orientation conditions. Both tasks required judgment of poser identity and indication of decision by pressing a reaction time button. Subjects were shown a set of photos in an Exposure Phase, followed by a Test Phase in which the photos previously seen (primed) were mixed with new photos (unprimed). The LTL subjects performed better than the RTL subjects for both the RT and accuracy data in both the Neutral and Affective Tasks. The performance of the LTL subjects improved when the task had an affective component (Affective vs. Neutral Task), whereas the RTL subjects did not show this benefit. In terms of specific emotions, for the LTL group, pain was responded to most slowly and shock was the emotion responded to most quickly, and significantly more quickly than in the RTL group. Fear was the emotion responded to most slowly by the RTL group and significantly more slowly when compared to the LTL group. The only priming effect was a reverse priming for pain, such that stimuli seen before were responded to less accurately than new stimuli; this was not related to lesion side.     

Perception and priming of affective faces in temporal lobectomy patients

Eighteen patients who had undergone standard anterior temporal lobectomy including removal of the amygdala and hippocampus (9 left, LTL; 9 right, RTL) were administered an Affective Task composed of faces depicting negative emotions, and a Neutral Task consisting of faces with different lighting and orientation conditions. Both tasks required judgment of poser identity and indication of decision by pressing a reaction time button. Subjects were shown a set of photos in an Exposure Phase, followed by a Test Phase in which the photos previously seen (primed) were mixed with new photos (unprimed). The LTL subjects performed better than the RTL subjects for both the RT and accuracy data in both the Neutral and Affective Tasks. The performance of the LTL subjects improved when the task had an affective component (Affective vs. Neutral Task), whereas the RTL subjects did not show this benefit. In terms of specific emotions, for the LTL group, pain was responded to most slowly and shock was the emotion responded to most quickly, and significantly more quickly than in the RTL group. Fear was the emotion responded to most slowly by the RTL group and significantly more slowly when compared to the LTL group. The only priming effect was a reverse priming for pain, such that stimuli seen before were respondedto less accurately than new stimuli; this was not related to lesion side.     

Performance of patients with unilateral temporal lobectomy on selective reminding procedures using either related or unrelated words

The present study compared the performance of patients with right (RTL) and left temporal lobectomy (LTL) with normal controls on two selective reminding procedures using either unrelated or semantically-related word-lists. LTL patients were found to be impaired relative to normal controls and RTL patients on both types of lists. The LTL patients entered fewer words into long-term storage (LTS) on each trial and showed a reduced ability to consistently recall such words on subsequent trials. The impaired initial learning of words and reduced subsequent recall of such words may reflect a unitary underlying deficiency. In addition, on the unrelated word-list, the LTL patients made significantly more intrusion errors than the other subject groups. Analyses of performance pattern indicate that LTL patients were able to benefit from the semantic-relatedness of words. RTL patients were impaired relative to normal controls on only the semantically-related word-list, both in entering words into LTS and the subsequent recall. These findings indicate that further studies of the semantic organization or its utilization of both RTL and LTL patients are warranted.     

Lateralized-temporal-lobe-lesion effects on learning and memory: examining the contributions of stimulus novelty and presentation mode

Previous studies have attributed poor memory for words after left temporal lobectomy (LTL) to a verbal memory deficit and poor memory for abstract designs after right temporal lobectomy (RTL) to a difficulty in remembering nonverbal/visual stimuli. In this investigation, the contribution of stimulus novelty to lateralised-lesion-effects was evaluated by testing list learning in 11 LTL, 8 RTL and 14 normal control subjects, using four types of material (familiar verbal, novel verbal, familiar designs and novel designs). In addition, the effect of presentation modality (spoken vs. written) on word-list learning was examined. We found that novelty enhanced material-specific-side-of lesion effects and that the LTL group had greater difficulty in learning spoken than written words.     

WMS-III performance in epilepsy patients following temporal lobectomy.

We examined performances on the Wechsler Memory Scale-3rd Edition (WMS-III) among patients who underwent temporal lobectomy for the control of medically intractable epilepsy. There were 51 right (RTL) and 56 left (LTL) temporal lobectomy patients. All patients were left hemisphere speech-dominant. The LTL and RTL patients were comparable in terms of general demographic, epilepsy, and intellectual/attention factors. Multivariate analyses revealed a significant crossover interaction (p <.001), with the RTL group scoring significantly lower on the visual than auditory indexes while the LTL group scored significantly lower on the auditory than visual memory indexes. Within-group pairwise analyses revealed statistically significant auditory versus visual index score comparisons (all p <.001) for both surgical groups. Discriminant analysis (p <.001) identified Verbal Paired Associates I, Faces I, and Family Pictures II to significantly discriminate RTL and LTL patients, with an overall correct classification rate of 81.3%. Our findings suggest that the WMS-III is sensitive to modality-specific memory performance associated with unilateral temporal lobectomy.     

A double dissociation in the affective modulation of startle in humans: effects of unilateral temporal lobectomy

In the present study we report a double dissociation between right and left medial temporal lobe damage in the modulation of fear responses to different types of stimuli. We found that right unilateral temporal lobectomy (RTL) patients, in contrast to control subjects and left temporal lobectomy (LTL) patients, failed to show potentiated startle while viewing negative pictures. However, the opposite pattern of impairment was observed during a stimulus that patients had been told signaled the possibility of shock. Control subjects and RTL patients showed potentiated startle while LTL patients failed to show potentiated startle. We hypothesize that the right medial temporal lobe modulates fear responses while viewing emotional pictures, which involves exposure to (emotional) visual information and is consistent with the emotional processing traditionally ascribed to the right hemisphere. In contrast, the left medial temporal lobe modulates fear responses when those responses are the result of a linguistic/cognitive representation acquired through language, which, like other verbally mediated material, generally involves the left hemisphere. Additional evidence from case studies suggests that, within the medial temporal lobe, the amygdala is responsible for this modulation.     

T-maze discrimination and reversal learning after unilateral temporal or frontal lobe lesions in man.

The interpretation of conditional discrimination and reversal learning as acquisition of declarative knowledge suggests that subjects with temporal lobe/hippocampal lesions are likely to be impaired on such tasks. Patients with unilateral left or right temporal lobectomy (and small hippocampal excisions) and patients with unilateral frontal lobe resections were compared with healthy controls on a discrimination reversal task, embedded in a computer game modelled on T-maze tasks traditionally used in animal experiments. The right temporal group showed a deficit in acquiring an initial conditional discrimination, and the frontal group tended to display a marginal impairment in discrimination reversal. These findings are compared with results from animal studies in terms of the mechanisms underlying reversal learning.     

Direction and distance deficits in path integration after unilateral vestibular loss depend on task complexity

The effects of peripheral vestibular disorders on the direction and distance components of the internal spatial representation were investigated. The ability of Menière's patients to perform path integration was assessed in different situations aimed at differentiating the level of spatial processing (simple versus complex tasks), the available sensory cues (proprioceptive, vestibular, or visual conditions), and the side of the path (towards the healthy versus the lesioned side). After exploring two legs of a triangle, participants were required either to reproduce the exploration path, to follow the reverse path, or to take a shortcut to the starting point of the path (triangle completion). Patients' performances were recorded before unilateral vestibular neurotomy (UVN) and during the time-course of recovery (1 week and 1 month) and were compared to those of matched control subjects tested at similar time intervals. Both the angular and linear path components of the trajectory were impaired for patients compared to controls. However, deficits were restricted to the complex tasks, which required a higher level of spatial processing. Most deficits were maximal 1 week after UVN, and some remained up to the first post-operative month. Spatial representation was differentially impaired according to the available sensory cues: deficits were absent in active locomotor blindfolded condition, appeared in conditions involving visual and vestibular information, and were maximal when visual cues alone were available. Finally, concerning the side of the path, unilateral vestibular loss led to global impairment of the internal spatial representation, yet some asymmetrical spatial performances were observed 1 week after UVN. On the whole, results suggest that the environment experienced by the patients is different after UVN and that a different internal spatial representation is constructed, especially for tasks requiring high levels of spatial processing.     

Learning and retention of melodic and verbal information after unilateral temporal lobectomy.

The role of the temporal lobes in auditory memory was tested in two analogous tasks assessing learning and 24-hr delayed recognition of unfamiliar melodies and nonsense words. The performance of patients with either anterior right (RT) or left (LT) temporal lobectomy was impaired in learning and delayed recognition of both melodies and words, as compared to normal control subjects, although some preserved learning over successive trials was observed. These results suggest a bilateral temporal-lobe contribution to the learning of these auditory patterns. However, melodies and nonsense words were not recognized in the same way by the two patient groups after 24 hr: subjects in the LT group tended to improve on melodies but drop on words, whereas subjects with RT lesions displayed the reverse pattern, suggesting a differential role for each temporal lobe in long-term memory, according to the nature of the cues inherent to a given type of stimulus.     

Prediction of cognitive change as a function of preoperative ability status among temporal lobectomy patients seen at 6-month follow-up

The relationship between preoperative ability levels and postoperative changes in cognitive function was examined among 23 left (LTL) and 19 right (RTL) temporal lobectomy patients using a battery of memory, language, and visuospatial tasks administered approximately 3 months before surgery and at 6 months follow-up. Higher preoperative performances on the memory and language measures were associated with larger decrements in postsurgical scores among the LTL patients. The RTL group showed no consistent relationship between preoperative ability levels and subsequent postsurgical cognitive changes. Based on the present data, we constructed base-rate tables for the Wechsler Memory Scale-Revised indicating the likelihood of measurable gains or losses in memory as a function of presurgical ability level for patients undergoing LTL. While tentative, these data provide a useful and practical guide for counseling prospective epilepsy patients of the attendant cognitive risks of LTL.     

Visual discrimination after anterior temporal lobectomy in humans

OBJECTIVE: To determine whether right anterior temporal lobectomy (RTL) results in perceptual deficits, and whether the perception of particular stimulus features (i.e., shape, motion, color) is affected differentially. BACKGROUND: RTL results in abnormal visual discrimination, recognition, and recall of pictorial material that cannot be easily specified verbally, such as designs and faces. It is unclear whether stimuli must be conceptually meaningful to elicit perceptual deficits. METHODS: Tests were constructed to assess a wide spectrum of basic visual discrimination abilities with simple, meaningless stimuli. The performance of nine patients who underwent left temporal lobectomy (LTL) and nine patients who underwent RTL were compared with that of normal control individuals. The mean excision size along lateral cortex was 3.7 cm for the LTL group and 5.6 cm for the RTL group; mean mesial excision size was 5.2 cm for LTL and 4.6 cm for RTL. RESULTS: Basic visual discrimination capacities were demonstrated to be essentially intact after LTL and RTL, except for a mild loss of blue color discrimination after RTL. CONCLUSIONS: There is little evidence that RTL produces perceptual impairments limited to the domain of pattern perception, or generalizable to nonmeaningful stimuli. The perceptual loss after RTL may be largely restricted to extraction of meaning, and related to the disruption of the circuits that connect the outcome of visual analysis to previously stored semantic information.     

Classical conditioning after temporal lobe lesions in man: sparing of simple discrimination and extinction.

Recent reports of impaired conditional discrimination learning in temporal lobectomy subjects have raised the question of response inhibition deficits in these patients. In the present study, left and right temporal lobectomy subjects and healthy controls completed an eyelid conditioning task, which required simple two-tone discrimination learning, followed by extinction. There were no group differences with regard to discrimination learning or extinction. General deficits in response inhibition are therefore not likely to account for the impairment in conditional discrimination observed in temporal lobectomy patients.     

Amygdala lesion in temporal lobe epilepsy subjects impairs associative learning of emotional facial expressions

To investigate the role of unilateral amygdala lesions on processing emotions, 22 drug-resistant temporal lobe epilepsy (TLE) subjects (12 with left-sided and ten with right-sided focus) were tested, after anterior temporal lobectomy or selective amygdalo-hippocampectomy on two associative learning tasks containing emotional and neutral facial expressions, respectively. Volumetric lesion analysis was performed on the basis of 3-D MR images. No effects of lesion side were found in TLE subjects. Taken the extent of amygdala damage into account, an interaction effect could be shown between task (learning of neutral facial expressions versus emotional facial expressions) and group (subjects with little versus considerable amygdala damage), indicating worse performance of subjects with considerable amygdala damage in learning emotional facial expressions. Subjects with considerable amygdala damage were also significantly impaired in learning emotional facial expressions when compared with control subjects.     

Distinct roles of hippocampus and medial prefrontal cortex in spatial and nonspatial memory

In earlier work, patients with hippocampal damage successfully path integrated, apparently by maintaining spatial information in working memory. In contrast, rats with hippocampal damage were unable to path integrate, even when the paths were simple and working memory might have been expected to support performance. We considered possible ways to understand these findings. We tested rats with either hippocampal lesions or lesions of medial prefrontal cortex (mPFC) on three tasks of spatial or nonspatial memory: path integration, spatial alternation, and a nonspatial alternation task. Rats with mPFC lesions were impaired on both spatial and nonspatial alternation but performed normally on path integration. By contrast, rats with hippocampal lesions were impaired on path integration and spatial alternation but performed normally on nonspatial alternation. We propose that rodent neocortex is limited in its ability to construct a coherent spatial working memory of complex environments. Accordingly, in tasks such as path integration and spatial alternation, working memory cannot depend on neocortex alone. Rats may accomplish many spatial memory tasks by relying on long‐term memory. Alternatively, they may accomplish these tasks within working memory through sustained coordination between hippocampus and other cortical brain regions such as mPFC, in the case of spatial alternation, or parietal cortex in the case of path integration. © 2016 Wiley Periodicals, Inc.     

Patterns of performance in amnesic subjects.

Patients with Korsakoff's syndrome, dementia, alcoholism, right and left temporal lobectomy, and normal subjects were compared on verbal learning and picture recognition memory tasks. Alcoholics and right lobectomy patients were similar on all measures, but the other groups had a characteristic pattern, particularly on hit and false positive rates in picture recognition.     

Footstep adjustments used to turn during walking in Parkinson's disease

Turning during walking is frequently problematic in Parkinson's disease (PD). The spatiotemporal characteristics of footstep adjustments used to turn 60 and 120 degrees were examined in 10 people with PD and 10 age, gender‐ and height‐matched control subjects, using three‐dimensional motion analysis. Control subjects used a recognizable pattern of spatial and temporal footstep modulations to turn. Participants with PD demonstrated significant differences in almost all variables. They (1) failed to turn as far as their peers; (2) showed a similar but scaled‐down pattern of spatial adjustments to turn; (3) used shorter strides when walking, with exaggerated reductions when turning; and (4) demonstrated small but significant temporal differences in step time adjustments. Group differences were more marked for the larger turn. Spatial results, interpreted in light of hypothesized basal ganglia dysfunction, are consistent with a normal motor command but impaired ability to maintain movement amplitude. Differences in adjustment of step time to turn may reflect impaired locomotor timing control in subjects with PD during challenging gait tasks. © 2008 Movement Disorder Society     

Memory disorders after unilateral cerebral lesions

In contrast to the amnestic syndrome, unilateral hemispheric lesions are mostly connected with selective memory deficits, which are related to either verbal or visual-spatial information. Clinical studies concerning this are mostly about patients with temporal lobe epilepsy. Almost all studies found that significantly worse verbal memory deficits appeared before or after left temporal lobectomy. In contrast to these outcomes, the results concerning right temporal lobectomy (RTL) are nonuniform. There are studies that cannot prove figurative memory deficits before or after RTL and others that ascertain a correlation between RTL and figurative memory deficits. Mean values are always compared with random samples of left and right hemispheric patients. In contrast, the presented study assumes a clinical isolated case and analyses a random sample of neurological patients with different genesis with a standardized memory test (Berlin Amnesia Test, or BAT). As a result, a significant correlation between left hemispheric lesions and verbal memory deficits as well as right hemispheric lesions and visual-spatial memory deficits can be proven. Possible reasons for these differing results with visual-spatial memory deficits are still under discussion.     

Effects of simultaneous vs sequential stimulus presentation on memory performance following temporal lobe resection in humans

This study examines the differential effects of simultaneous vs sequential stimulus presentation on performance of a visuo-spatial memory task in patients following unilateral temporal lobectomy for relief of complex-partial seizures. Eleven subjects with surgical resection of the left temporal lobe, 13 subjects with surgical resection of the right temporal lobe, and 12 normal controls were examined. Results indicate that both the Right and the Left surgical groups were impaired on the visuo-spatial memory task employed. Further, the Right resection group was significantly more impaired for the recall of stimuli presented in the sequential condition as compared to the simultaneous condition.     

Hippocampectomized rats are impaired in homing by path integration

Theoretical, behavioral, and electrophysiologic evidence suggests that the hippocampal formation may play a role in path integration, a form of spatial navigation in which an animal can return to a starting point by integrating self-movement cues generated on its outward journey. The present study examined whether the hippocampus (Ammon's horn and the dentate gyrus) is involved in this form of spatial behavior. Control rats and rats with selective ibotenic acid lesions of the hippocampus were tested in a foraging task in which they retrieved large food pellets from an open field, which when found, they carried to a refuge for consumption. The experiments measured the rats' homing accuracy, returning to the starting location, under conditions in which visual, surface, and self-movement cues; surface and self-movement cues; or only self-movement cues were available. Although both control rats and rats without a hippocampus could use visual and surface cues, only control rats appeared to be able to use self-movement cues. The finding that hippocampal rats are impaired under conditions requiring the use of self-movement cues suggests that the hippocampus plays an essential role in path integration.