Hypohedonia in schizophrenia.

The affective disorder in schizophrenia is an important manifestation of the schizophrenic illness. Such clinical features of joylessness, interpersonal aversion, and affective blunting have been considered by Rado and Meehl to represent a neurophysiological deficit in pleasure capacity which they termed anhedonia, but is more aptly characterized by the term hypohedonia. A free-recall task employing 24 affectively laden words presented in random order over nine trials was given to a carefully selected group of nonpsychotic hospitalized schizophrenics, hospitalized nonschizophrenics, and normals. The results of the study demonstrate that normals remember pleasant words to a significantly greater extent than upleasant words. This Pollyanna tendency or the tendency to utilize pleasant words over upleasant words has been described by Osgood as a stable cross-cultural phenomenon. By contrast, the schizophrenics show a significantly lower recall of pleasant words when compared with normals, although they remember unpleasant words to a comparable degree as normals. These findings provide experimental support for the hypohedonia hypothesis in schizophrenia. The nonshcizophrenic patients recall pleasant and unpleasant words to a significantly greater degree than neutral words. They are thus affectively governed in the free-recall task and seem equally sensitized to both pleasant and unpleasant affect in their mnemonic processing.     

Clinical and etiological implications of a specific attention deficit in schizophrenia

Forty-seven psychiatric inpatients, including 26 schizophrenics and 21 nonschizophrenics, were measured on four clinical factors (chronicity, premorbid adjustment, reported symptomatology, and diagnosis) and four indices of reaction time (RT) performance (mean RT, RT variance, and redundancy-associated deficit [RAD] at 3- and 7-second preparatory intervals [PIs] ). Each clinical factor was analyzed in turn as a dependent variable in multiple regression analyses. The RT indices comprised the predictor set in each multiple regression. RAD at 7-second PI is related to chronicity for psychiatric patients in general and for schizophrenic patients in particular. Diagnosis and premorbid adjustment are related primarily to mean RT. No evidence was found that RAD is an artifact of high intertrial variance or long RT latencies, but intertrial variance does play a role in moderating the implications of RAD. The different correlations within schizophrenic and nonschizophrenic groups suggest a) that the Elgin Scale has a different meaning when used with schizophrenics than with nonschizophrenics, and b) that it is not useful to treat schizophrenic and nonschizophrenic disorders on the same continuum. The results in general suggest that the vulnerability factor thought to be associated with RAD militates for greater chronicity across different types of patients. The RAD effect within schizophrenics is nevertheless relatively greater than within other patients.     

Hemispheric asymmetry in visual recognition of words and motor response in schizophrenic and depressive patients.

Two-letter Hangul words were presented tachistoscopically as target words to either the right or left visual field of normal subjects, schizophrenics, and depressive patients. The subjects' task was to judge the similarity or difference between the target words and the words used for comparison. They were to signal as soon as possible by pressing a key with their hands. In normal subjects, the correct response rate was significantly higher in the left hemisphere; there was little difference in the speed of motor response between the two hemispheres, however. Compared with normal subjects, both patient groups showed generalized impairment. Schizophrenia was associated with impairment in the left hemisphere, depression was associated with impairment in the right hemisphere.     

Voluntary movement dysfunction in schizophrenics

Several aspects of fine motor control were compared in schizophrenics and two control populations. The motor behavior analyzed was a button-press response in a forced choice paradigm. Three areas of abnormality were seen in schizophrenics: first, the interval preceding the motor response was characterized by reduced motor steadiness prior to the button-press response; second, the motor response was made with excessive force (hyperdynamia); and third, the agonist-antagonist synchrony (motor reversal) was impaired. Schizophrenics on and off neuroleptics did not differ on any measure of motor control, but schizophrenics with clinically observed tardive dyskinesia were found to have significantly less steadiness prior to the motor response than other schizophrenics.     

Functional links between motor and language systems

Transcranial magnetic stimulation (TMS) was applied to motor areas in the left language-dominant hemisphere while right-handed human subjects made lexical decisions on words related to actions. Response times to words referring to leg actions (e.g. kick) were compared with those to words referring to movements involving the arms and hands (e.g. pick). TMS of hand and leg areas influenced the processing of arm and leg words differentially, as documented by a significant interaction of the factors Stimulation site and Word category. Arm area TMS led to faster arm than leg word responses and the reverse effect, faster lexical decisions on leg than arm words, was present when TMS was applied to leg areas. TMS-related differences between word categories were not seen in control conditions, when TMS was applied to hand and leg areas in the right hemisphere and during sham stimulation. Our results show that the left hemispheric cortical systems for language and action are linked to each other in a category-specific manner and that activation in motor and premotor areas can influence the processing of specific kinds of words semantically related to arm or leg actions. By demonstrating specific functional links between action and language systems during lexical processing, these results call into question modular theories of language and motor functions and provide evidence that the two systems interact in the processing of meaningful information about language and action.     

Metacognition and false recognition in patients with frontal lobe lesions: the distinctiveness heuristic

The distinctiveness heuristic is a response mode in which participants expect to remember vivid details of an experience and make recognition decisions based on this metacognitive expectation. Whereas much is known about the cognitive processes that are involved in using the distinctiveness heuristic, little is known about the corresponding brain processes. Because such metacognitive processes that involve the evaluation and control of one's memory are believed to be dependent upon the frontal lobes, the authors examined whether the distinctiveness heuristic could be engaged to reduce false recognition in a repetition lag paradigm in patients with lesions of their frontal lobes. Half of the participants studied pictures and corresponding auditory words; the other half studied visual and auditory words. Studied and novel items were presented at test as words only, with all novel items repeating after varying lags. Controls who studied pictures were able to reduce their false recognition of repeated lag items relative to those controls who studied words, demonstrating their use of the distinctiveness heuristic. Patients with frontal lobe lesions showed similar levels of false recognition regardless of whether they studied pictures and words or words only, suggesting that they were unable to use the distinctiveness heuristic. The authors suggest that the distinctiveness heuristic is a metacognitive strategy, dependent upon the frontal lobes, that may be engaged by healthy individuals to reduce their false recognition.     

The Emotional Stroop task: A comparison between schizophrenic subjects and controls

The colour-word Emotional Stroop task (ES task) has been proposed to assess the interferences between emotion and attention. Using this task, first, we examined how attention (using reaction times) can be modified by emotionally relevant words in schizophrenics as compared with controls as a function of the emotional significance of the word; second, we tested the assumption that schizophrenics with the most negative symptoms will show higher impairment in relationship to negative emotional words. In general, schizophrenics were slower to react. In both groups, mean reaction times were slower for emotional as compared with neutral words. No significant differences were observed between negative and positive words either in schizophrenics (n = 21) or in controls (n = 20). Even in the most negative schizophrenic patients, there were no differences between negative and positive words. There were no significant interactions between type of stimulus and any clinical variables (PANSS negative or non negative categorization, etc.). Also, there were no statistically significant correlations between reaction times and neuroleptic dosage or anhedonia scores. In conclusion, schizophrenia patients showed the same degree of interference from emotional words as compared with controls. Moreover, patients with a higher level of negative symptoms did not differently experience positive and negative words.     

Electrophysiological estimates of the time course of semantic and phonological encoding during listening and naming

Current psycholinguistic models suggest that we know what we want to say before we decide how we are going to say it: in other words, for speaking, word meaning is activated prior to information about syntax and phonology. Listening likely involves the reverse order of processes: phonological processing before meaning activation. We examined the relative time courses of phonological and semantic processing during language production and comprehension using event-related brain potentials (ERPs). Participants viewed a series of pictures (with the instruction to covertly name the depicted item), or heard a series of words, and made dual choice Go/noGo decisions based on each item's conceptual (whether the item was an animal or an object) and phonological features (whether the item's German name started with a vowel or a consonant). During picture naming, the N200 component (related to response inhibition) indicated that conceptual processing preceded phonological processing by about 170ms. During auditory word processing, on the other hand, the brain activity related to these two aspects of comprehension indicated some temporal overlap with the N200 to phonological processing preceding that to semantic processing by only about 85ms. In sum, the data are compatible with current psycholinguistic models of speech production and comprehension and argue for serial or widely spaced cascaded processing during production but more parallel processing of information during comprehension.     

Amodal semantic representations depend on both anterior temporal lobes: Evidence from repetitive transcranial magnetic stimulation

The key question of how the brain codes the meaning of words and pictures is the focus of vigorous debate. Is there a “semantic hub” in the temporal poles where these different inputs converge to form amodal conceptual representations? Alternatively, are there distinct neural circuits that underpin our comprehension of pictures and words? Understanding words might be primarily left-lateralised, linked to other language areas, while semantic representation of pictures may be more bilateral. To elucidate this debate, we used offline, low-frequency, repetitive transcranial magnetic stimulation (rTMS) to disrupt neural processing temporarily in the left or right temporal poles. During the induced refractory period, participants made judgements of semantic association for verbal and pictorial stimuli. The efficiency of semantic processing was reduced by rTMS, yet a perceptual task of comparable difficulty was unaffected. rTMS applied to the left or right temporal poles disrupted semantic processing for words and pictures to the same degree, while rTMS delivered at a control site had no impact. The results confirm that both temporal poles form a critical substrate within the neural network that supports conceptual knowledge, regardless of modality.     

Number magnitude determines gaze direction: Spatial-numerical association in a free-choice task

Since Dehaene et al. (1993) reported the SNARC (Spatial–Numerical Association of Response Codes) effect, researchers have repeatedly documented an influence of number magnitude on reaction time in various motor tasks. In addition, thinking about numbers induces shifts of visuo-spatial attention (Fischer et al., 2003). The present study examined whether number magnitude affects a person’s eye movement in a free-choice task. After the presentation of a number in the middle of the screen, two pictures of human faces were simultaneously presented on either side of the screen. Participants were asked to explore the screen after the presentation of a number. Analyses performed on first eye fixations confirmed that number magnitude affects gaze direction in this free-choice task. The present study shows that the influence of number magnitude on visuo-spatial attention affects the choice of where to look first.     

Decision and action planning signals in human posterior parietal cortex during delayed perceptual choices

During simple perceptual decisions, sensorimotor neurons in monkey fronto‐parietal cortex represent a decision variable that guides the transformation of sensory evidence into a motor response, supporting the view that mechanisms for decision‐making are closely embedded within sensorimotor structures. Within these structures, however, decision signals can be dissociated from motor signals, thus indicating that sensorimotor neurons can play multiple and independent roles in decision‐making and action selection/planning. Here we used functional magnetic resonance imaging to examine whether response‐selective human brain areas encode signals for decision‐making or action planning during a task requiring an arbitrary association between face pictures (male vs. female) and specific actions (saccadic eye vs. hand pointing movements). The stimuli were gradually unmasked to stretch the time necessary for decision, thus maximising the temporal separation between decision and action planning. Decision‐related signals were measured in parietal and motor/premotor regions showing a preference for the planning/execution of saccadic or pointing movements. In a parietal reach region, decision‐related signals were specific for the stimulus category associated with its preferred pointing response. By contrast, a saccade‐selective posterior intraparietal sulcus region carried decision‐related signals even when the task required a pointing response. Consistent signals were observed in the motor/premotor cortex. Whole‐brain analyses indicated that, in our task, the most reliable decision signals were found in the same neural regions involved in response selection. However, decision‐ and action‐related signals within these regions can be dissociated. Differences between the parietal reach region and posterior intraparietal sulcus plausibly depend on their functional specificity rather than on the task structure.     

A brief note on serum calcium levels in schizophrenics and controls

The present investigation examined the relationship between serum calcium levels and schizophrenic disorder. Unlike earlier studies a wider range of diagnoses was surveyed, subjects were limited to first time admission, and the relationship of socio-demographic factors to the hypothesized biological risk factor was assessed. Analysis revealed no significant differences in levels of serum calcium between schizophrenics and four nonschizophrenic comparison groups, nor were any one of several socio-demographic factors found to correlate significantly with serum values. Some risk factors, however, differentiated between schizophrenics and nonschizophrenics. They were being single, poor employment history, and reason for admission. A more promising avenue for further research in the area is outlined.     

The effect of motion content in action naming by Parkinson's disease patients

IntroductionThe verb-specific impairment present in patients with motion-related neurological diseases has been argued to support the hypothesis that the processing of words referring to motion depends on neural activity in regions involved in motor planning and execution. We presented a group of Parkinson’s disease (PD) patients with an action-naming task in order to test whether the prevalence of motion-related semantic content in different verbs influences their accuracy.MethodsForty-nine PD patients and 19 healthy seniors participated in the study. All of PD participants underwent a neurological and neuropsychological assessment to rule out dementia. Subjective ratings of the motion content level of 100 verbs were obtained from 14 young voluntaries. Then, pictures corresponding to two subsets of 25 verbs with significantly different degrees of motor component were selected to be used in an action-naming task. Stimuli lists were matched on visual and psycholinguistic characteristics.ResultsANOVA analysis reveals differences between groups. PD patients obtained poor results in response to pictures with high motor content compared to those with low motor association. Nevertheless, this effect did not appear on the control group. The general linear mixed model analytic approach was applied to explore the influence of the degree of motion-related semantic content of each verb in the accuracy scores of the participants. The performance of PD patients appeared to be negatively affected by the level of motion-related semantic content associated to each verb.ConclusionsOur results provide compelling evidence of the relevance of brain areas related to planning and execution of movements in the retrieval of motion-related semantic content.     

Motor control of schizophrenics--II. Manual control and tracking: sensory and motor deficits

Manual control and tracking of 12 acute and chronic schizophrenics was tested for comparison with their performance in oculomotor tracking. Schizophrenics tended to be slower in a non-timed, non-tracking hand movement, and chronics made even slower movement when the experimental room was illuminated than when it was darkened. Chronics also had a significantly higher reaction time than normal controls. When tracking a constant-velocity visual target, all schizophrenics were significantly slower than normals to high-velocity (50 degrees and 60 degrees/s) targets only. When tracking a sinusoidally moving target, schizophrenics were not less accurate over-all but they showed less improvement than normals when room illumination gave visual information about background and hand position. This complex group of motor deficiencies of schizophrenics, along with their oculomotor control problems, suggests that they have sensory processing, attentional, and motor planning problems when performing orienting tasks.     

Electrophysiological evidence for reduced latent inhibition in schizophrenic patients

The present study examined latent inhibition (LI) effects in 17 acute and 16 partially remitted schizophrenic patients, and in 20 healthy controls, by measuring manual response latencies and event-related potentials (ERPs) during an association learning task. ERPs were recorded to elucidate the role of attention in the LI effect. Subjects performed a go/no-go task with an auditory conditional stimulus predicting a visual go command. Half of the subjects in each diagnostic group were pre-exposed to the conditional stimulus which had been used as an irrelevant distractor in a preceding discrimination task. Independent of diagnostic group membership, pre-exposed subjects showed slower manual responses to go stimuli than non-pre-exposed subjects, reflecting a robust LI effect. The N100 wave after the conditional stimuli, however, showed a differential pattern: pre-exposure increased N100 amplitudes in acute schizophrenics, whereas pre-exposed control subjects showed a trend for decreased N100. The amplitude of the contingent negative variation (CNV) was unaffected by pre-exposure. The ERP results suggest that acute schizophrenics have a deficit in learned inattention to irrelevant stimuli. However, the intact LI effect in schizophrenics at the motor speed level shows that human LI is a complex phenomenon depending on the tasks and measures used.     

Motor persistence and inhibition in autism and ADHD.

The present study compared performance of children with Attention-Deficit/Hyperactivity Disorder (ADHD) and high functioning autism (HFA) with that of controls on 4 tasks assessing 2 components of motor control: motor response inhibition and motor persistence. A total of 136 children (52 ADHD, 24 HFA, 60 controls) ages 7 to 13 years completed 2 measures of motor inhibition (Conflicting Motor Response and Contralateral Motor Response Tasks) and 2 measures of motor persistence (Lateral Gaze Fixation and NEPSY Statue). After controlling for age, IQ, gender, and basic motor speed, children with ADHD performed significantly more poorly than controls on the Conflicting Motor Response and Contralateral Motor Response Tasks, as well as on Statue. In contrast, children with HFA achieved lower scores than controls only on measures of motor persistence, with no concomitant impairment on either motor inhibition task. These results are consistent with prior research that has demonstrated relatively spared motor inhibition in autism. The findings highlight the utility of brief assessments of motor control in delineating the unique neurobehavioral phenotypes of ADHD and HFA.     

Action verbs and the primary motor cortex: a comparative TMS study of silent reading, frequency judgments, and motor imagery

Single pulse transcranial magnetic stimulation (TMS) was applied to the hand area of the left primary motor cortex or, as a control, to the vertex (STIMULATION: TMS(M1) vs. TMS(vertex)) while right-handed volunteers silently read verbs related to hand actions. We examined three different tasks and time points for stimulation within the same experiment: subjects indicated with their left foot when they (i) had finished reading, (ii) had judged whether the corresponding movement involved a hand rotation after simulating the hand movement, and (iii) had judged whether they would frequently encounter the action verb in a newspaper (TASK: silent reading, motor imagery, and frequency judgment). Response times were compared between TMS(M1) and TMS(vertex), both applied at different time points after stimulus onset (DELAY: 150, 300, 450, 600, and 750 ms). TMS(M1) differentially modulated task performance: there was a significant facilitatory effect of TMS(M1) for the imagery task only (about 88 ms), with subjects responding about 10% faster (compared to TMS(vertex)). In contrast, response times for silent reading and frequency judgments were unaffected by TMS(M1). No differential effect of the time point of TMS(M1) was observed. The differential effect of TMS(M1) when subjects performed a motor imagery task (relative to performing silent reading or frequency judgments with the same set of verbs) suggests that the primary motor cortex is critically involved in processing action verbs only when subjects are simulating the corresponding movement. This task-dependent effect of hand motor cortex TMS on the processing of hand-related action verbs is discussed with respect to the notion of embodied cognition and the associationist theory.     

The effect of picture priming on event-related potentials of normal and disabled readers during a word recognition memory task

Normal and one subtype of disabled readers were compared in their visual event-related potentials (ERPs) that were elicited by primed and unprimed words during a recognition memory task. The primed words were preceded by a picture having the same denotative meaning, while unprimed words were preceded by a picture having a non-associated meaning. Normal readers exhibited consistently greater amplitude than the disabled readers to unprimed words with a negative wave at 455 ms (N400). For the disabled readers, this N400 was evident, though somewhat smaller, than for controls, at fronto-central placements, but absent at the lateral parietal and occipital sites. Priming a word with a picture reduced N400 amplitude for both the normal and disabled readers. There were no remarkable differences between groups in their ERPs to the pictures. The pattern of ERP results obtained seems to reflect a failure of this subtype of disabled readers to engage long-term, semantic memory, while their short-term linguistic processing is intact.     

Cross-modal integration and conceptual categorization in baboons

This study investigates concept formation and cross-modal integration in baboons. Response times were recorded in a categorical task involving discrimination between human and baboon vocalizations. We show that a brief presentation of human or baboon prime pictures conceptually related to the target sound shortened response speed of one baboon. Cross-modal priming effects were replicated with degraded pictures, and were also found in a sample of humans. Cross-modal priming demonstrates that this baboon had formed amodal abstract concepts of the human and baboon categories.     

Apparent response incompatibility effects on P3 latency depend on the task

Ten young women were tested with an ERP paradigm that used the words 'left,' 'right,' 'LEFT,' 'RIGHT' as stimuli. The stimulus sequence was presented as several separate runs with varying response instructions. Subjects were instructed to respond according to the meaning of the stimulus in the (WORD task), to the case in which the stimulus was written (CASE task), or to both the case and meaning of the stimulus (CASE/WORD) task. In each task, half the trials called for a response that was incompatible with the stimulus. For the WORD task, compatible and incompatible trials were presented as separate blocks of trials. For all 3 tasks an additional stimulus sequence was presented in which the words were degraded with superimposed visual random noise. Reaction time (RT) in the CASE/WORD task was more than 100 msec later than in the other tasks. In the WORD and CASE/WORD tasks, RT was delayed more than 100 msec when the response was incompatible with the stimulus. Degrading the stimulus additionally delayed RT by about 100 msec. In the WORD and CASE tasks, error RTs were earlier than correct RTs. P3 latency was measured with a single-trial latency adjustment algorithm. P3 latency was delayed in the CASE/WORD task compared to the other 2 tasks. P3 was delayed by degrading the stimuli. Contrary to some previous reports, P3 was delayed by about 70 msec when incompatible responses were required, but only in the WORD task. Taken together with error and RT data, these P3 latency data are consistent with the notion that the task causes subjects to adopt different strategies and hence different types of processing (i.e., serial vs. parallel). Depending on the type of processing, P3 may appear to be affected by response incompatibility.