Nonverbal Amnesia and Asymmetric Cerebral Lesions Following Encephalitis

Global amnesia after herpes simplex encephalitis has been typically associated with lesions of anterior and medial temporal lobe, inferior and medial frontal lobe, and insula. The neuropathologic correlates of this disease are usually considered to be bilateral and similar across cases. We describe a 27-year-old woman whose chronic amnesia and cerebral lesions after viral encephalitis indicate a different pattern. Two features distinguish her presentation: (1) markedly asymmetric lesions extensively involving the right temporal lobe but sparing almost all of the same structures on the left and (2) severe compromise of nonverbal learning and a nonverbal retrograde amnesia in contrast to disproportionately small impairments of verbal learning and retention. The findings suggest that encephalitis patients cannot be treated as a homogeneous group and that detailed analysis of variability in their anatomic lesions may be an important explanatory factor in neural accounts of these severe human amnesias.     

Nonverbal priming in amnesia

In this experiment, we examined whether a group of well-characterized amnesic patients would exhibit normal priming for novel nonverbal materials after a single exposure. Both amnesic patients and normal control subjects studied line figures and were then given a priming test in which they were asked to reproduce both old (studied) and new (unstudied) figures after a brief exposure. The measure of priming was the number of old patterns drawn correctly relative to the number of new patterns drawn correctly. Both subject groups reproduced more old patterns than new patterns, and the effect was similar in the two groups. In contrast, amnesic patients were significantly impaired on a recognition memory test for the items that had been presented. This study contributes to recent evidence that implicit memory can support the rapid acquisition of novel verbal and nonverbal information. Perceptual priming for such material is independent of the structures damaged in amnesia.     

Age-related changes in verbal and nonverbal memory during early childhood

In the present experiment, age-related changes in verbal and nonverbal memory performance by 2- to 4-year-old children were assessed. All children participated in the same unique event, and their memory of that event was assessed after a 24-hr delay. Overall, children's performance on each memory measure increased as a function of age. Furthermore, children's performance on both the verbal and nonverbal memory tests was related to their language ability; children with more advanced language skills reported more during the verbal interview and exhibited superior nonverbal memory relative to children with less advanced language skills. Finally, children's verbal recall of the event lagged behind both their nonverbal recall and their general verbal skill. It is hypothesized that despite large strides in language acquisition. preschool-age children continue to rely primarily on nonverbal representations of past events. The findings have important implications for the phenomenon of childhood amnesia.     

The use of visual and verbal memory processes by three-year-old children

Nonverbal (imagery) materials become more effective than verbal materials in aiding memory as age increases; indeed, children under five years have shown superior memory for verbal over nonverbal materials. The present study points out and changes four commonalities in the design of studies finding this latter relationship in an attempt to determine if nonverbal materials would prove superior to verbal ones. Four six-item paired-associate lists were presented individually using a study-test procedure. Presentation of the lists involved either pictures, words, or both. Recognition was tested either verbally or visually.Results indicated that the combined visual-verbal study materials produced performance superior to visual materials alone, which in turn were superior to verbal materials alone. Recognition of pictures was superior to recognition of words, regardless of mode of input. The relationship of these results to the procedural changes made are discussed, along with implications for current hypotheses of children's use of imagery.     

Iconic reading in a case of alexia without agraphia caused by a brain tumor: a tachistoscopic study

The lack of nonverbal reading comprehension in the clinical disconnection syndrome, alexia without agraphia, has been contradictory to the relative reading comprehension of the right hemisphere in split brains. We report a 39-year-old patient with verbal alexia without agraphia caused by brain tumor. On rapid tachistoscopic presentation of object names, he denied seeing anything but showed nonverbal reading comprehension by pointing to the corresponding objects. He lost this ability when he recovered ability to name individual letters of the object names. Our results suggest that even partial verbal reading such as the naming of single letters makes demonstration of iconic reading impossible and that total functional disconnection from verbalization, as initially noted in this case or in split brain studies, is necessary to show nonverbal reading comprehension.     

Verbal and nonverbal recognition memory in aphasic and nonaphasic stroke patients

The ability to retain lists of verbal and nonverbalizable items across recurrent recognition tasks was tested in three groups: (1) stroke patients with a left-brain lesion and aphasia, (2) stroke patients with a right-brain lesion and left hemiplegia, and (3) nonneurologically impaired outpatients. As determined with signal detection measures, aphasics were deficient in discriminating words that were to be remembered from those that were not; their recognition of nonverbal visual (geometric art) or auditory (bird calls) patterns, however, was unimpaired. Left hemiplegics showed the opposite pattern. After a long-term interval (<10 min), correct recognition of words was diminished in all groups whereas recognition of visual patterns increased. Both groups of stroke patients adopted material-specific decision criteria which in part accounted for the dissociation of verbal and nonverbal recognition memory by laterality of lesion. Item analysis indicated that aphasics' verbal memory difficulties were affected by acoustic-semantic confusion of list words.     

The retrieval hypothesis as an explanation of induced retrograde amnesia

The present experiment tested the hypothesis that retrograde induced amnesia is due to retrieval failure and anterograde induced amnesia to encoding failure by providing recall cues which were expected to eliminate retrograde amnesia but worsen or have no effect on anterograde amnesia. The 80 subjects received auditory presentation of 10 lists, each composed of 15 four-letter words presented at a rate of 2s/item at 75 dB in a free-recall task, followed by a 72 s recall period. The amnesia-producing event was an outstanding item in serial position 8 presented at 115 dB (about the intensity of a loud shout) on half the lists. During the first half of the recall period subjects free-recalled, but during the last half they were given a list of the first (single cue) or the first two (double cue) letters of each word, to be used as aids to recall. To demonstrate induced amnesia, lists containing a loud item were compared to those not containing one. First half free recall performance indicated that large retrograde and anterograde effects were present for both cue conditions. Second half cued recall performance indicated that in the double cue condition retrograde amnesia disappeared and anterograde amnesia became larger. Cueing had much smaller effects in the single cue condition.     

Working and long-term memory deficits in schizophrenia: is there a common prefrontal mechanism?

This study tested the hypothesis that dorsolateral prefrontal cortex deficits contribute to both working memory and long-term memory disturbances in schizophrenia. It also examined whether such deficits were more severe for verbal than nonverbal stimuli. Functional magnetic resonance imaging was used to assess cortical activation during performance of verbal and nonverbal versions of a working memory task and both encoding and recognition tasks in 38 individuals with schizophrenia and 48 healthy controls. Performance of both working memory and long-term memory tasks revealed disturbed dorsolateral prefrontal cortex activation in schizophrenia, although medial temporal deficits were also present. Some evidence was found for more severe cognitive and functional deficits with verbal than nonverbal stimuli, although these results were mixed.     

Child Compliance and Congruity between Verbal and Nonverbal Maternal Communication — A Methodological Note

This paper is a report of a study of congruity between verbal and nonverbal maternal communication with sons during two 30-minute sessions. The instructions to the mothers varied for the two sessions by increasing the time the mother was asked to spend on a brain teaser game and by decreasing the number of play materials available for the sons in the second session. The two sessions were videotaped through a one-way mirror and rated independently for maternal verbal and nonverbal communicaiton and child compliance. Mothers differed for the two sessions in their communication with their sons. The study demonstrated that maternal nonverbal communication, as well as verbal communication, can be reliably measured through use of videotape recording.     

Continuous executive function disruption interferes with application of an information integration categorization strategy

Category learning is often characterized as being supported by two separate learning systems. A verbal system learns rule-defined (RD) categories that can be described using a verbal rule and relies on executive functions (EFs) to learn via hypothesis testing. A nonverbal system learns non-rule-defined (NRD) categories that cannot be described by a verbal rule and uses automatic, procedural learning. The verbal system is dominant in that adults tend to use it during initial learning but may switch to the nonverbal system when the verbal system is unsuccessful. The nonverbal system has traditionally been thought to operate independently of EFs, but recent studies suggest that EFs may play a role in the nonverbal system—specifically, to facilitate the transition away from the verbal system. Accordingly, continuously interfering with EFs during the categorization process, so that EFs are never fully available to facilitate the transition, may be more detrimental to the nonverbal system than is temporary EF interference. Participants learned an NRD or an RD category while EFs were untaxed, taxed temporarily, or taxed continuously. When EFs were continuously taxed during NRD categorization, participants were less likely to use a nonverbal categorization strategy than when EFs were temporarily taxed, suggesting that when EFs were unavailable, the transition to the nonverbal system was hindered. For the verbal system, temporary and continuous interference had similar effects on categorization performance and on strategy use, illustrating that EFs play an important but different role in each of the category-learning systems.     

Functional amnesia: clinical description and neuropsychological profile of 10 cases

We carried out the first neuropsychological study of a series of patients with functional amnesia. We evaluated 10 patients, first with a neurological examination and then with three tests of anterograde amnesia and four tests of retrograde amnesia. Excluding one patient who later admitted to malingering, all patients had a significant premorbid psychiatric history and one or more possible precipitating factors for their amnesia. Eight of the 10 patients still had persistent retrograde amnesia at our last contact with them (median = 14 mo after the onset of amnesia). On tests of anterograde amnesia, the patients performed normally as a group, though some patients scored poorly on tests of verbal memory. On tests of retrograde amnesia, all patients had difficulty re-collecting well-formed autobiographical memories of specific events from their past. In contrast, patients performed as well as controls at distinguishing the names of cities from fictitious city names. On remote memory tests for past public events and famous faces, different patients exhibited different but internally consistent patterns of impaired and spared performance. The variability in the clinical and neuropsychological findings among our patients may be understood by supposing that memory performance is poor in proportion to how directly a test appears to assess a patient's common sense concept of memory. The presentation of patients with functional amnesia is as variable as humankind's concept of what memory is and how it works.     

The von Restorff effect and induced amnesia: production by manipulation of sound intensity.

When an outstanding item appears in an otherwise homogeneous list of items, the outstanding item is better remembered (the von Restorff effect), and items before and after it may be more poorly remembered (induced amnesia) than corresponding items in a control list. In the present experiments the outstanding item was a word presented as a loud shout among other words presented at normal conversational levels. In two experiments, large retrograde- and anterograde-induced amnesiae effects were demonstrated using a free-recall and a recognition task. In both experiments half of the subjects were told what to expect and were instructed to devise a strategy to eliminate induced amnesia. These instructions failed to eliminate the amnesiac effect. A third experiment was designed to demonstrate an empirical similarity between induced and clinical amnesia. In clinical retrograde (but not anterograde) amnesia, "lost" memories are sometimes recovered with time. Filled delays of 0, 30, or 120 sec interpolated between list presentation and recall demonstrated that induced retrograde amnesia disappeared at the longest delay but induced anterograde amnesia was unchanged. A fourth experiment eliminated some alternate interpretations of the effect.     

The impact of object working memory on timing

Nontemporal information processing involving short-term memory requirements disturbs time estimation. Previous studies mostly used letters or digits, which are maintained in working memory by phonological loops. Since verbal and nonverbal information are processed by separate working-memory subsystems, how do nonverbal, object-based memory tasks affect time estimation? We manipulated visual object memory load using the magic cube materials. Participants were divided into three groups, who completed a reaction-time task (control task), a memory-recognition task interposed by an attempt to produce a 2500-ms time interval (active processing), and a memory-recognition task following time interval production (passive retention). The produced time increased with increasing memory-object size under both the active processing and passive retention conditions; mean produced time interval did not significantly differ between the two experimental conditions. By comparing the reaction times and error rates of a relevant task, we excluded any speed–accuracy tradeoff during timing. This result suggests that when the working-memory information to be processed includes objects requiring attention for retention, the production of time intervals is also affected by memory item maintenance.     

Directed forgetting of visual symbols: Evidence for nonverbal selective rehearsal

Is selective rehearsal possible for nonverbal information? Two experiments addressed this question using the item method directed forgetting paradigm, where the advantage of remember items over forget items is ascribed to selective rehearsal favoring the remember items. In both experiments, difficult-to-name abstract symbols were presented for study, followed by a recognition test. Directed forgetting effects were evident for these symbols, regardless of whether they were or were not spontaneously named. Critically, a directed forgetting effect was observed for unnamed symbols even when the symbols were studied under verbal suppression to prevent verbal rehearsal. This pattern indicates that a form of nonverbal rehearsal can be used strategically (i.e., selectively) to enhance memory, even when verbal rehearsal is not possible.     

The effect of response choice relatedness on pantomime and verbal recognition ability in aphasic patients

Twenty aphasic and twenty control subjects were examined on two versions of a pantomime recognition and a verbal recognition test; one version containing response choices conceptually/semantically related to target responses, the other containing unrelated response choices. The aphasic group was inferior to controls on the pantomime and verbal recognition tests, although the magnitude and consistency of the differences between aphasics and controls were greater for the pantomime test. The presence of conceptually/semantically related response choices on the pantomime recognition test significantly reduced test scores of aphasic patients, and this reduction was related to the magnitude of the effect of response choice relatedness on their verbal recognition test performance. The findings are consistent with an interpretation of aphasia as an impairment of a central symbolic ability which can affect processing for meaning in both verbal and nonverbal modes of communication.     

Hemispheric differences in stimulus identification

Subjects were presented with either verbal (letters) or nonverbal (outline forms) stimuli to their left or right cerebral hemispheres. Verbal items presented with a lateral masking stimulus were identified more quickly and accurately when presented to the right hemisphere rather than to the left. When the letters were presented without a masking stimulus, weak hemispheric effects were obtained. Nonverbal forms demonstrated faster reaction time and fewer errors for right-hemisphere presentations under both masked and unmasked conditions. Retinal locus of the display item was also varied and produced faster responding with fewer errors when the stimulus was presented foveally rather than peripherally under all display conditions. These effects were attributed to the use of a manual response procedure that effectively reduced the ability of subjects to employ names for the stimulus objects.     

Amnestic disorders and their role in cognitive theory

Amnesia refers to a disorder of memory, and classical amnesia with continuous problems in aquiring new information is the most studied type of amnesia. The integration into a memory systems model of clinical studies of classical amnesia, cognitive theory, and studies with neuroimaging methods is one of the prime success stories in modern cognitive neuroscience. The clinical spectrum of amnesia encompasses a wide range of disorders ranging from specific encoding deficits for language or visuospatial information to psychogenic amnesia with confusion and loss of memory for personal identity. Two cases are reviewed, one with selective verbal amnesia and the other with focal retrograde amnesia, presenting some puzzles and challenges to current modular thinking about memory that may lead to theoretical advances. An interactive model emphasizing the communication between brain codes and regions in memory may have promise.     

Visual imagery ability and the recognition of verbal and nonverbal stimuli.

High and low visual imagers, defined as such primarily on the basis of spatial manipulation test performance, were required to identify tachistoscopically-presented pictures, concrete words, and abstract words varying in familiarity. Two recognition paradigms were employed, recognition threshold and recognition latency. High imagers were faster in picture recognition under both paradigms when a nonverbal set or strategy was primed and when pictures were relatively unfamiliar in the threshold paradigm. No relationship was found between imagery ability and word recognition in the visual modality, nor was visual imagery ability related to the auditory recognition of verbal and nonverbal stimuli, such as words and environmental sounds. Commonalities between these findings and others in the imagery ability literature were noted.     

Remote memory in a patient with circumscribed amnesia

It has been suggested that extensive and severe remote memory loss is not a component of a circumscribed amnesic syndrome but may be attributable to problem solving and retrieval deficiencies associated with the frontal lobe damage which is present in some amnesic patients. In order to assess this notion, retrograde amnesia was studied in a patient, W.H., who had no apparent cortical damage revealed by radiological examination, and who evidenced no major cognitive deficiency other than amnesia. Regardless of whether remote memory was measured by recall or recognition procedures, patient W.H. exhibited impaired memory for information from the 1960s, 1970s, and 1980s, but was unimpaired in retrieving information from the 1940s and 1950s. These results demonstrate that retrograde amnesia can occur in patients who have a circumscribed memory deficit.