Comments on neuropsychological evaluation of epilepsy surgery: are the tests sensitive enough?

Epileptic lesions often affect two of the most important functions in human behavior, memory and emotion. While cognitive functions, e.g, speech and memory, are normally carefully studied, emotional and psychosocial aspects of behavior are often overlooked in the pre- and postoperative evaluation of epilepsy patients. In my comment, I will address the need for methodological and theoretical refinement, especially regarding measurements of emotional and psychosocial aspects. In evaluating memory functions, a functionalistic approach is suggested; that is, in contrast to the entity view, studies should focus on the interaction between task demands and the available cognitive capabilities of the rememberer. We should develop a broad set of tests and demonstrate dissociations between different tasks that tap different capabilities and different memory systems: we should look for patterns of results rather than single scores.

The accuracy of the dichotic, the visual half-field, and the intracarotid sodium amytal memory tests in preoperative neuropsychological investigation of epileptic patients.

Three methods for determining the lateralization of memory functions in patients with pharmacologically resistant intractable partial epilepsy were compared and evaluated. The three methods studied were a dichotic memory test, a visual half-field memory test, and an intracarotid Sodium Amytal memory test. A total of 35 epileptic patients considered for surgical therapy and a group of 20 non-epileptic control subjects took part in the study. The results show that the three tests tap different memory functions and that each of the test pick up a memory dysfunction in the hemisphere indicated by EEG recordings. In combination with an extensive neuropsychological test battery, the three methods produce data that concur with the evaluation made of EEG recordings.

Preoperative and postoperative memory testing of epileptic patients.

The present paper has four main objectives. First, it proposes a general theoretical orientation of memory functions as a basis for the research to be discussed. This framework is functionalistic/interactionistic in nature, in that memory is seen as an interaction between available cognitive capabilities of the individual and specific demands of the situation in which the individual is to remember a certain set of materials. Secondly, on the basis of this framework certain methodological requirements are discussed. These considerations take into account the need for a proper analysis of the to-be-remembered (TBR) information and those cognitive functions involved in remembering the TBR information presented. Thirdly, a preoperative and postoperative memory test is presented. This was designed on the basis of the theoretical and methodological considerations mentioned. Data from one such ongoing study is presented, taking into account various measures of memory functions; immediate free recall, final free recall, final cued recall, serial recall, final final free recall, short-term memory and long-term memory capacity as measured by the Tulving & Colotla [1] lag measure, primacy, asymptote and recency effects, and semantic memory. Finally, on the basis of the experience from this memory test a few aspects of memory testing in epileptic patients are suggested for future research.

Pre- and postoperative memory of dichotically presented words in patients with complex partial seizures.

Dichotic listening tests were used to determine cerebral hemisphere memory functions in patients with complex partial seizures before, 10 days after, and 1-3 yr after right (RTE) or left (LTE) temporal-lobe excisions. Control subjects were also tested on two occasions. The tests consisted of presenting a series of 12-word lists and 7-word lists alternately to the two ears while backward speech was presented to the other ear. Measures of immediate free recall, final free recall, final cued recall, and serial recall were employed. The results revealed: (a) that both groups of patients were inferior the control group in tests tapping long-term memory functions rather than short-term memory functions, (b) a right-ear advantage for RTE patients at postoperative testing, (c) that the LTE group was more affected by surgery than the RTE group, and (d) a general improvement in recall performance from early to late postoperative testing. Taken together, these results indicate that the present dichotic test can be used as a non-invasive hemisphere memory test to complement invasive techniques for diagnosis of patients considered for epilepsy surgery.

Emotional stress and eyewitness memory: a critical review.

The eyewitness literature often claims that emotional stress leads to an impairment in memory and, hence, that details of unpleasant emotional events are remembered less accurately than details of neutral or everyday events. A common assumption behind this view is that a decrease in available processing capacity occurs at states of high emotional arousal, which, therefore, leads to less efficient memory processing. The research reviewed here shows that this belief is overly simplistic. Current studies demonstrate striking interactions between type of event, type of detail information, time of test, and type of retrieval information. This article also reviews the literature on memory for stressful events with respect to two major theories: the Yerkes-Dodson law and Easter-brook's cue-utilization hypothesis. To account for the findings from real-life studies and laboratory studies, this article discusses the possibility that emotional events receive some preferential processing mediated by factors related to early perceptual processing and late conceptual processing.

Hemisphere memory of concrete and abstract information determined with the intracarotid Sodium Amytal test.

An extended version of the bilateral intracarotid Sodium Amytal test was administered pre-operatively to 13 patients with intractable complex partial epileptic seizures, to determine cerebral hemisphere speech and memory. There were 6 patients with left temporal lobe lesions and 7 patients with right temporal lobe lesions. Amobarbital (175 mg, 10%), injected on 2 occasions, determined the left hemisphere to be speech dominant in all cases. Memory assessed with recall, cued recall, and recognition of concrete/abstract words and pictures, was studied on 3 occasions: in a baseline test considered to indicate the degree of patient cooperation and the bilateral hemisphere memory; in a right hemisphere Amytal test; and in a left hemisphere Amytal test. The specific data pattern obtained, that abstract pictorial information is most efficiently processed by an intact right hemisphere and that verbal information is processed best by an intact left hemisphere, demonstrates the reliability of the approach taken here to present abstract and concrete to be remembered information.

Eye fixations and memory for emotional events.

Subjects watched either an emotional, neutral, or unusual sequence of slides containing 1 critical slide in the middle. Experiments 1 and 2 allowed only a single eye fixation on the critical slide by presenting it for 180 ms (Experiment 1) or 150 ms (Experiment 2). Despite this constraint, memory for a central detail was better for the emotional condition. In Experiment 3, subjects were allowed 2.70 s to view the critical slide while their eye movements were monitored. When subjects who had devoted the same number of fixations were compared, memory for the central detail of the emotional slide was again better. The results suggest that enhanced memory for detail information of an emotional event does not occur solely because more attention is devoted to the emotional information.

An improved optical eye movement detector for visual half-field studies of cerebral hemisphere memory.

An instrument for the evaluation of cerebral hemisphere memory using the visual half-field (VHF) technique is described. The object was to improve the existing VHF-techniques by means of an infra-red eye movement detector to control visual fixation, and to automatically control the presentation of visual stimuli. The instrument consists of four functional parts; visual presentation; optical eye movement control; electronic programming; and reaction time measuring. The instrument has been used on normal controls and in neuropsychological pre- and post-operative investigations on patients with drug resistant partial epilepsy. It has proved easy to use and reveals valuable information about hemisphere memory function. The use of an optical eye movement detector together with electronic logic has improved the accuracy and reliability of the VHF-test. A schematic outline of the instrument and a brief description of electronic circuitry are given.

Intergroup biases and eyewitness testimony.

The study examined how the in-group/out-group status of a perpetrator of a distinctly violent crime might influence an eyewitness's evaluation of his behavior and a witness's performance in an identification task. Immigrant and Swedish students saw a film showing a simulated robbery, with an immigrant or a Swede as the perpetrator. Results showed that both groups evaluated an ethnically dissimilar perpetrator as more culpable than an ethnically similar perpetrator. In a line-up task, both immigrant and Swedish participants mistakenly identified an innocent immigrant more often than an innocent Swede. Participants' biased evaluations of the perpetrator are discussed in terms of cognitive and motivational mechanisms. Expectations regarding the typical ethnicity of a perpetrator of this type of crime are suggested to account for the findings of the line-up task.

Flashbulb memories: special, but not so special.

This study deals with flashbulb memories associated with the assassination of the Swedish prime minister Olof Palme. A major goal of this research was to explore the consistency of such memories through comparison of the subjects' recollections on two different occasions, one year apart. The results obtained indicated that flashbulb events are accurately recalled in terms of a narrative conception of the concomitant circumstances of the event, but that the event descriptions are not consistent with respect to the specific details of these circumstances. It was concluded that the loss of information during one year contradicts the notion that flashbulb memories persist in absolute accuracy over time, as has been claimed in previous studies. Rather, these memories appear to be reconstructions based on residuals of the circumstances concomitant with the specific event (i.e., that of first hearing of the shocking news), and these memories follow the same pattern of recollection as does recollection of other autobiographical and laboratory-induced emotional events.

The role of age on reactivity and memory for emotional pictures.

The purpose of this study was to investigate subjects' reactivity to emotional pictures and their recollection of these pictures, and to examine these two factors as they relate to age. Adolescents and young adults were shown emotionally arousing scenic pictures for long (4-s) and very brief (50-ms) durations. Recognition of the pictures and recall and recognition of words presented along with the pictures were assessed both immediately after the presentation and six weeks later. The results showed that very negative pictures are retained better than neutral or even positive pictures, and that very negative pictures reduce memory for associated information. It was also found that adolescents show a somewhat lower reactivity to very negative pictures and a higher degree of retention of these pictures than adults. The results are discussed in relation to (a) habituation effects, (b) strategies that subjects might develop to block emotional involvement, and (c) the notion that watching violence might serve as a powerful prime to socially undesirable behaviour.

The fate of traumatic memories in childhood and adulthood.

The present article addresses issues concerning the complex relation between memory and trauma in childhood and adult life. Research findings showing how children and adults remember public and personal emotional events are presented, and mechanisms functioning to hold traumatic memories back from awareness are discussed. In the final section, developmental aspects are addressed by considering the interplay between child and adult trauma. Several cases are described that show how childhood trauma may be represented in memory and influence later development and adult memory processes.

Hemisphere memory differences in Sodium Amytal testing of epileptic patients.

Material-specific memory performance was studied by a Sodium Amytal testing procedure in order to diagnose hemispheric memory functions in 27 patients with unilateral temporal or frontal epileptic lesions who were under consideration for surgical therapy. Memory was tested for concrete and abstract words, pictures of common objects, figures, and faces, presented pre- and post-inactivation of the hemisphere contralateral or ipsilateral to the epileptic focus. The results showed that tests involving words and pictures of common objects were conclusive about hemispheric memory functions, in showing cross-over interactions between side of lesion and side of injection. Figures and faces were hemisphere discriminative to a much lesser degree (only a minor preference for the right hemisphere was found) and are presumably more dependent on the functional integrity of both hemispheres. The present findings demonstrate that hemispheric memory functions can be studied in more detail with the Amytal technique than has been shown hitherto in the literature.

Hemisphere inactivation and mood-state changes.

Mood-state changes were studied during a sodium Amytal testing procedure in epilepsy patients with unilateral temporal lobe foci. The results showed that inactivation of the left hemisphere, but not the right hemisphere, produced a negative mood state. This decline in mood was not specifically related to side of focus or sex. As expected, the inactivation of either hemisphere also lead to an impairment in memory performance. This impairment was somewhat worse during a left than a right hemisphere inactivation. Furthermore, patients with left hemisphere foci showed a lower memory performance than patients with a right-hemisphere lesion. These results suggest (a) a hemispheric specialization for emotion that underlie changes in mood and (b) a discrepancy between mood states at encoding (during inactivation) and retrieval (after inactivation).

Visual half-field testing for defining cerebral hemisphere speech laterality.

The purpose of this study was to investigate to what extent the noninvasive visual half-field (VHF) test can reliably determine cerebral speech dominance for the individual patient with partial epilepsy considered for surgical treatment. The present VHF test consisted of a list of 36 words presented correctly and mirrored in the lateral visual fields to 13 right-handed and 14 left-handed control subjects and to 14 right-handed and 2 left-handed patients with partial epilepsy. In the controls, it was found that all right-handed and 10 out of 14 left-handed control subjects showed a right VHF (i.e., left hemisphere) advantage. Three of the left-handed control subjects showed the opposite pattern, and one showed no visual field advantage. All of the right-handed patients showed a right VHF advantage, except one who showed no VHF advantage. The two left-handed patients had both a left VHF advantage. Intracarotid amytal speech testing documented left hemisphere speech dominance in all right-handed patients. Of the two left-handed patients, one had right-sided, the other bilateral speech representation. The results suggest that the present VHF test reliably predicts cerebral hemisphere speech in patients with epilepsy.

Amnesia and vegetative abnormalities after irradiation treatment: a case study.

This paper describes a case of a patient (GX) with a brain tumour in the third ventricle who developed a syndrome of amnestic disorder and vegetative abnormalities (hyperphagia, oligodipsia) after irradiation treatment that followed brain surgery. The patient shows an extremely poor long-term memory on both visually and verbally presented material, and of autobiographical events occurring after the onset of the illness, but some preserved memory functions on short-term memory tasks, semantic memory tasks, and implicit memory tasks. Given the onset of symptoms only after irradiation (a memory deficit in particular), and the non-invasive nature of the surgery, the probable etiology is post-irradiation syndrome.

Hemispheric asymmetry effects in children studied by dichotic listening and visual half-field testing.

Dichotic listening (DL) and visual half-field (VHF) testing were used to study hemisphere asymmetry in a developmental perspective. Five-, 8-, and 11-year-old children were presented lists of fused words using a DL technique in Experiment 1, and 8- and 11-year-old children were presented pictures of common objects using a VHF technique in Experiment 2. In both experiments, measures of identification, free recall, and recognition of the words/pictures were employed. The results revealed effects of ear input (right-ear advantage) and half-field presentation (right visual half-field advantage) for all age groups, although the magnitude of this lateralization effect differed between the three memory measures. The results are discussed in relation to developmental aspects of language laterality, and in relation to the clinical utility of non-invasive lateralization techniques.