The cerebellum's role in reading: a functional MR imaging study.
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BACKGROUND AND PURPOSE: Long considered to have a role limited largely to motor-related functions, the cerebellum has recently been implicated as being involved in both perceptual and cognitive processes. Our purpose was to determine whether cerebellar activation occurs during cognitive tasks that differentially engage the component processes of word identification in reading. METHODS: Forty-two neurologically normal adults underwent functional MR imaging of the cerebellum with a gradient-echo echo-planar technique while performing tasks designed to study the cognitive processing used in reading. A standard levels-of-processing paradigm was used. Participants were asked to determine whether pairs of words were written in the same case (orthographic processing), whether pairs of words and non-words rhymed with each other, respectively (phonologic assembly), and whether pairs of words belonged to the same category (semantic processing). Composite maps were generated from a general linear model based on a randomization of statistical parametric maps. RESULTS: During phonologic assembly, cerebellar activation was observed in the middle and posterior aspects of the posterior superior fissure and adjacent simple lobule and semilunar lobule bilaterally and in posterior aspects of the simple lobule, superior semilunar lobule, and inferior semilunar lobule bilaterally. Semantic processing, however, resulted in activation in the deep nuclear region on the right and in the inferior vermis, in addition to posterior areas active in phonologic assembly, including the simple, superior semilunar, and inferior semilunar lobules. CONCLUSION: The cerebellum is engaged during reading and differentially activates in response to phonologic and semantic tasks. These results indicate that the cerebellum contributes to the cognitive processes integral to reading. (+info)
Reading, equivalence, and recombination of units: a replication with students with different learning histories.
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First graders, preschoolers, special education students, and adults received a reading program in which they learned to match printed to dictated words and to construct (copy) printed words. The students not only learned to match the training words but also learned to read them. In addition, most of the students learned to read new words that involved recombinations of the syllables of the training words. The results replicate and extend the generality of a prior analysis of a reading program based on stimulus equivalence and recombination of units. (+info)
Increased discrimination of "false memories" in autism spectrum disorder.
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Individuals with autism spectrum disorder (ASD) have impaired ability to use context, which may manifest as alterations of relatedness within the semantic network. However, impairment in context use may be more difficult to detect in high-functioning adults with ASD. To test context use in this population, we examined the influence of context on memory by using the "false memory" test. In the false memory task, lists of words were presented to high-functioning subjects with ASD and matched controls. Each list consists of words highly related to an index word not on the list. Subjects are then given a recognition test. Positive responses to the index words represent false memories. We found that individuals with ASD are able to discriminate false memory items from true items significantly better than are control subjects. Memory in patients with ASD may be more accurate than in normal individuals under certain conditions. These results also suggest that semantic representations comprise a less distributed network in high-functioning adults with ASD. Furthermore, these results may be related to the unusually high memory capacities found in some individuals with ASD. Research directed at defining the range of tasks performed superiorly by high-functioning individuals with ASD will be important for optimal vocational rehabilitation. (+info)
Disturbance of semantic processing in temporal lobe epilepsy demonstrated with scalp ERPs.
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We investigated event-related potentials (N400, LPC and CNV) elicited in temporal lobe epilepsy (TLE) patients and control subjects from scalp electrodes, using a word-pair category matching paradigm. Each prime consisted of a Japanese noun (constructed from 2-4 characters of the Hiragana) followed by a Chinese character (Kanji) as the target, the latter representing one of five semantic categories. There were two equally probable target conditions: match or mismatch. Each target was preceded by a prime, either belonging to, or not belonging to, the same semantic category. The subjects were required to respond with a specified button press to the given target, according to the condition. We found RTs to be longer under the mismatch condition in both subject groups. The N400 amplitude was reduced in TLE subjects under both conditions, although LPC and CNV amplitudes showed no significant differences. These results suggest that scalp N400 is capable of demonstrating disturbance of semantic processing in TLE non-invasively. (+info)
The mere exposure effect in patients with schizophrenia.
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The mere exposure effect refers to the development of an emotional preference for previously unfamiliar material because of frequent exposure to that material. This study compared schizophrenia subjects (n = 20) to normal controls (n = 21) to determine whether implicit memory, as demonstrated by the mere exposure effect, was intact. Patients with schizophrenia demonstrated a normal preference for both verbal and visual materials seen earlier relative to novel materials, despite impaired performance on a recognition task for explicit memory using similar materials. Previous studies of schizophrenia subjects have shown a dissociation between implicit and explicit memory on verbal tasks. We found a similar dissociation demonstrated by normal functioning on an implicit memory task and impaired functioning on an explicit memory task. Potential implications of these findings are discussed with regard to treatment and rehabilitation. (+info)
Cognitive disturbance in outpatient depressed younger adults: evidence of modest impairment.
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BACKGROUND: Investigations of cognitive disturbances among patients with mood disorders have yielded inconsistent results. Although marked neuropsychologic deficits have been reported in elderly patients and in midlife patients with severe depression, the severity of cognitive impairments in medically healthy younger ambulatory adults with depression has not been well characterized. METHODS: A comprehensive battery of standard neuropsychologic tests and experimental computerized measures of cognitive functioning were administered to unmedicated ambulatory younger adults with mild to moderate nonbipolar depression and to a group of age- and gender-equated healthy subjects. RESULTS: Patients demonstrated a notable absence of widespread cognitive impairment. Deficits in executive functions were observed on the Wisconsin Card Sort Test but not on several other tests. Despite the absence of significant impairment on tests of attention, memory, and motor performance in the total sample, symptom severity and age of illness onset were correlated with poorer performance on some tests of cognitive functioning even after correction for age. CONCLUSIONS: These findings, derived from a large sample of unmedicated depressed outpatients, indicate that major depressive disorder in healthy younger ambulatory adults does not cause appreciable impairments in cognitive functioning in the absence of clinical and course-of-illness features. (+info)
Investigation of cerebral dominance in 'left-handers' and 'right-handers' using unilateral electroconvulsive therapy.
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Twenty-four patients receiving unilateral electroconvulsive therapy for depression were given the first treatment with electrodes on the left or right side of the head and the second treatment with electrodes on the opposite side. They were tested with the Word Associate Learning subtest of the Wechsler Memory Scale when fully responsive after the first ECT and after the same time interval following the second ECT. Twelve were left-handed and 12 were right-handed writers. In both groups, better scores were usually obtained after right-sided treatment. Redistribution of patients into sinistral, mixed, and dextral groups showed that this difference between the effects of left and right-sided ECT was significant only in dextrals. Only two right-handed writers had scores indicating right-sided dominance for speech; both were 'shifted sinistrals'. Left hemisphere dominance was indicated in 67% of all non-dextrals. Eight of nine patients in whom testing was repeated after a second pair of treatments on alternate sides obtained scores favouring the same side in both pairs of testing. Findings indicate the need for closer inquiry into handedness than is often made before unilateral ECT is prescribed. Further development of unilateral ECT for establishing cerebral dominance in individuals is supported by the results. (+info)
Pairing-induced changes of orientation maps in cat visual cortex.
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We have studied the precise temporal requirements for plasticity of orientation preference maps in kitten visual cortex. Pairing a brief visual stimulus with electrical stimulation in the cortex, we found that the relative timing determines the direction of plasticity: a shift in orientation preference toward the paired orientation occurs if the cortex is activated first visually and then electrically; the cortical response to the paired orientation is diminished if the sequence of visual and electrical activation is reversed. We furthermore show that pinwheel centers are less affected by the pairing than the pinwheel surround. Thus, plasticity is not uniformly distributed across the cortex, and, most importantly, the same spike time-dependent learning rules that have been found in single-cell in vitro studies are also valid on the level of cortical maps. (+info)