Visual exploration in Parkinson's disease and Parkinson's disease dementia.

Parkinson's disease, typically thought of as a movement disorder, is increasingly recognized as causing cognitive impairment and dementia. Eye movement abnormalities are also described, including impairment of rapid eye movements (saccades) and the fixations interspersed between them. Such movements are under the influence of cortical and subcortical networks commonly targeted by the neurodegeneration seen in Parkinson's disease and, as such, may provide a marker for cognitive decline. This study examined the error rates and visual exploration strategies of subjects with Parkinson's disease, with and without cognitive impairment, whilst performing a battery of visuo-cognitive tasks. Error rates were significantly higher in those Parkinson's disease groups with either mild cognitive impairment (P = 0.001) or dementia (P < 0.001), than in cognitively normal subjects with Parkinson's disease. When compared with cognitively normal subjects with Parkinson's disease, exploration strategy, as measured by a number of eye tracking variables, was least efficient in the dementia group but was also affected in those subjects with Parkinson's disease with mild cognitive impairment. When compared with control subjects and cognitively normal subjects with Parkinson's disease, saccade amplitudes were significantly reduced in the groups with mild cognitive impairment or dementia. Fixation duration was longer in all Parkinson's disease groups compared with healthy control subjects but was longest for cognitively impaired Parkinson's disease groups. The strongest predictor of average fixation duration was disease severity. Analysing only data from the most complex task, with the highest error rates, both cognitive impairment and disease severity contributed to a predictive model for fixation duration [F(2,76) = 12.52, P ≤ 0.001], but medication dose did not (r = 0.18, n = 78, P = 0.098, not significant). This study highlights the potential use of exploration strategy measures as a marker of cognitive decline in Parkinson's disease and reveals the efficiency by which fixations and saccades are deployed in the build-up to a cognitive response, rather than merely focusing on the outcome itself. The prolongation of fixation duration, present to a small but significant degree even in cognitively normal subjects with Parkinson's disease, suggests a disease-specific impact on the networks directing visual exploration, although the study also highlights the multi-factorial nature of changes in exploration and the significant impact of cognitive decline on efficiency of visual search.

Evaluation of Biopesticides for Management of Bemisia tabaci Middle East-Asia Minor 1 (Hemiptera: Aleyrodidae) in Florida.

The sweetpotato whitefly, Bemisia tabaci MEAM1, is a pest known to significantly impact tomato development and yields through direct damage and virus transmission. To manage this pest, the current study compared the effectiveness of various insecticide rotations. Field trials included rotations involving synthetic insecticides, biochemicals, and microbial agents, applied according to their highest labeled concentrations. The results indicated that while standard synthetic insecticides consistently reduced whitefly egg and nymph counts significantly, microbial biopesticide rotations also achieved reductions, although less consistently. This study demonstrated that while traditional chemical treatments remain highly effective, microbial biopesticides containing Beauveria bassiana and Cordyceps javanica present a viable alternative to manage MEAM1 in tomato fields. The data generated in this study provided baseline information for further investigations to determine the potential for optimizing integrated pest management (IPM) and insecticide resistance management (IRM) strategies by incorporating microbial biopesticides in rotations with a variety of modes of action to sustainably manage B. tabaci MEAM1 populations in agricultural settings.

Monitoring the susceptibility of Bemisia tabaci Middle East-Asia Minor 1 (Hemiptera: Aleyrodidae) to afidopyropen, cyantraniliprole, dinotefuran, and flupyradifurone in south Florida vegetable fields.

Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) is a significant pest that damages a wide range of high-value vegetable crops in south Florida. This pest has demonstrated the ability to develop resistance to various insecticide groups worldwide. Monitoring the resistance levels of MEAM1 populations and maintaining baseline susceptibility data are crucial for the long-term effectiveness of insecticide management strategies. We conducted serial dilution bioassays on 15 field populations of MEAM1 collected in south Florida to assess their resistance to 4 key insecticides: afidopyropen, cyantraniliprole, dinotefuran, and flupyradifurone. To quantify resistance levels, resistance ratios (RR) were generated by comparing the LC50 values of field populations to those of a known susceptible MEAM1 colony reared in the laboratory. Our findings reveal that all field-collected populations were susceptible to dinotefuran (RR 1-8) and flupyradifurone (RR 2-8). While over 80% of the populations tested were susceptible to afidopyropen (RR 1-9), 2 populations exhibited low (RR 38) and moderate resistance (RR 51), respectively. In contrast, most of the populations (57%) showed low to moderate resistance to cyantraniliprole (RR 21-78), and the remaining populations were susceptible (RR 3-10). The 2 populations with resistance to afidopyropen also exhibited moderate resistance to cyantraniliprole. Further research in this direction can aid in refining insecticide resistance management programs in Florida and other regions where B. tabaci MEAM1 is a major pest. Exploring the implications of these findings will be essential for insecticide use and integrated pest management strategies in south Florida.

Keeping an eye on the truth? Pupil size changes associated with recognition memory.

During recognition memory tests participants' pupils dilate more when they view old items compared to novel items. We sought to replicate this "pupil old/new effect" and to determine its relationship to participants' responses. We compared changes in pupil size during recognition when participants were given standard recognition memory instructions, instructions to feign amnesia, and instructions to report all items as new. Participants' pupils dilated more to old items compared to new items under all three instruction conditions. This finding suggests that the increase in pupil size that occurs when participants encounter previously studied items is not under conscious control. Given that pupil size can be reliably and simply measured, the pupil old/new effect may have potential in clinical settings as a means for determining whether patients are feigning memory loss.

IQ as a predictor of functional outcome in schizophrenia: a longitudinal, four-year study of first-episode psychosis.

Studies of established schizophrenia have consistently found that cognitive function predicts social and clinical outcomes. The findings from first-episode studies have been more variable, with only some studies reporting predictive relationships. We tested the possibility that an index of general cognitive ability, IQ, may be a more sensitive and reliable predictor of outcome in first-episode schizophrenia than specific measures of memory and executive function. Fifty-four patients with first-episode schizophrenia or schizoaffective disorder were assessed for cognitive and social function as well as symptoms at three time points over the four years following first presentation of their psychotic illness. Regression analyses were performed to determine whether IQ and specific neuropsychological measures at first episode and one-year follow-up predicted four-year social function and residual symptoms. The effects of premorbid and concurrent IQ on outcome were also assessed. Premorbid IQ and IQ at each assessment significantly predicted social function at four-year follow-up. This relationship remained significant after the social function or symptom scores at first presentation were accounted for in the regression. Specific measures predicted certain domains of social function, but these were weaker and less consistent than IQ. The predictive values of cognition on residual symptoms were less strong; the most consistent finding was a relationship between IQ and the negative syndrome. This study suggests that early in the course of schizophrenia, general cognitive ability, as measured by IQ, is a more sensitive and reliable predictor of functional outcome than measures of specific ability.

The effects of task instructions on pro and antisaccade performance.

In the antisaccade task participants are required to overcome the strong tendency to saccade towards a sudden onset target, and instead make a saccade to the mirror image location. The task thus provides a powerful tool with which to study the cognitive processes underlying goal directed behaviour, and has become a widely used index of "disinhibition" in a range of clinical populations. Across two experiments we explored the role of top-down strategic influences on antisaccade performance by varying the instructions that participants received. Instructions to delay making a response resulted in a significant increase in correct antisaccade latencies and reduction in erroneous prosaccades towards the target. Instructions to make antisaccades as quickly as possible resulted in faster correct responses, whereas instructions to be as spatially accurate as possible increased correct antisaccade latencies. Neither of these manipulations resulted in a significant change in error rate. In a second experiment, participants made fewer errors in delayed pro and antisaccade tasks than in a standard antisaccade task. The implications of these results for current models of antisaccade performance, and the interpretation of antisaccade deficits in clinical populations are discussed.

Hypnotic suggestibility, cognitive inhibition, and dissociation.

We examined two potential correlates of hypnotic suggestibility: dissociation and cognitive inhibition. Dissociation is the foundation of two of the major theories of hypnosis and other theories commonly postulate that hypnotic responding is a result of attentional abilities (including inhibition). Participants were administered the Waterloo-Stanford Group Scale of Hypnotic Susceptibility, Form C. Under the guise of an unrelated study, 180 of these participants also completed: a version of the Dissociative Experiences Scale that is normally distributed in non-clinical populations; a latent inhibition task, a spatial negative priming task, and a memory task designed to measure negative priming. The data ruled out even moderate correlations between hypnotic suggestibility and all the measures of dissociation and cognitive inhibition overall, though they also indicated gender differences. The results are a challenge for existing theories of hypnosis.

Age differences in emotion recognition skills and the visual scanning of emotion faces.

Research suggests that a person's emotion recognition declines with advancing years. We examined whether or not this age-related decline was attributable to a tendency to overlook emotion information in the eyes. In Experiment 1, younger adults were significantly better than older adults at inferring emotions from full faces and eyes, though not from mouths. Using an eye tracker in Experiment 2, we found young adults, in comparison with older adults, to have superior emotion recognition performance and to look proportionately more to eyes than mouths. However, although better emotion recognition performance was significantly correlated with more eye looking in younger adults, the same was not true in older adults. We discuss these results in terms of brain changes with age.

What's good for the goose is not good for the gander: Age and gender differences in scanning emotion faces.

OBJECTIVES: Research indicates that older adults' (≥60 years) emotion recognition is worse than that of young adults, young and older men's emotion recognition is worse than that of young and older women (respectively), older adults' looking at mouths compared with eyes is greater than that of young adults. Nevertheless, previous research has not compared older men's and women's looking at emotion faces so the present study had two aims: (a) to examine whether the tendency to look at mouths is stronger amongst older men compared with older women and (b) to examine whether men's mouth looking correlates with better emotion recognition. METHOD: We examined the emotion recognition abilities and spontaneous gaze patterns of young (n = 60) and older (n = 58) males and females as they labelled emotion faces. RESULTS: Older men spontaneously looked more to mouths than older women, and older men's looking at mouths correlated with their emotion recognition, whereas women's looking at eyes correlated with their emotion recognition. DISCUSSION: The findings are discussed in relation to a growing body of research suggesting both age and gender differences in response to emotional stimuli and the differential efficacy of mouth and eyes looking for men and women.

Drug expectancy is necessary for stimulus control of human attention, instrumental drug-seeking behaviour and subjective pleasure.

BACKGROUND: It has been suggested that drug-paired stimuli (S+) control addictive behaviour by eliciting an explicit mental representation or expectation of drug availability. AIMS: The aim of the present study was to test this hypothesis by determining whether the behavioural control exerted by a tobacco-paired S+ in human smokers would depend upon the S+ eliciting an explicit expectation of tobacco. DESIGN: In each trial, human smokers (n=16) were presented with stimuli for which attention was measured with an eyetracker. Participants then reported their cigarette reward expectancy before performing, or not, an instrumental tobacco-seeking response that was rewarded with cigarette gains if the S+ had been presented or punished with cigarette losses if the S- had been presented. Following training, participants rated the pleasantness of stimuli. RESULTS: The S+ only brought about conditioned behaviour in an aware group (those who expected the cigarette reward outcome when presented with the S+). This aware group allocated attention to the S+, performed the instrumental tobacco-seeking response selectively in the presence of the S+ and rated the S+ as pleasant. No conditioned behaviour was seen in the unaware group (those who did not expect the cigarette reward outcome in the presence of the S+). CONCLUSIONS: Drug-paired stimuli control selective attention, instrumental drug-seeking behaviour and positive emotional state by eliciting an explicit expectation of drug availability.

Contingency knowledge is necessary for learned motivated behaviour in humans: relevance for addictive behaviour.

AIMS: Many forms of human conditioned behaviour depend upon explicit knowledge of the predictive contingency between stimuli, responses and the reinforcer. However, it remains uncertain whether the conditioning of three key behaviours in drug addiction-selective attention, instrumental drug-seeking behaviour and emotional state--are dependent upon contingency knowledge. To test this possibility, we employed an avoidance procedure to generate rapidly these three forms of conditioned behaviour without incurring the methodological problems of drug conditioning. DESIGN: In two experiments, participants (16 students) were trained on a schedule in which one stimulus (S +) predicted the occurrence of a startling noise, which could be cancelled by performing an instrumental avoidance response. MEASUREMENTS: The allocation of attention to the S + and the rate and probability of the avoidance response in the presence of S + were measured. Following training, participants were tested for their knowledge of the stimulus-noise contingencies arranged in the study and rated the emotional qualities of the stimuli. FINDINGS: Both experiments showed that S + gained control of selective attention, instrumental avoidance behaviour and subjective anxiety, but only in participants who reported explicit knowledge of the Pavlovian contingency between the S + and the startling noise. CONCLUSIONS: The implication of the present findings is that the control of selective attention, instrumental drug-seeking behaviour and emotional state by drug-paired stimuli is mediated by cognitive knowledge of the predictive contingency between the stimulus and the drug.

Effect of Transcranial Direct Current Stimulation on Prefrontal Inhibition in Schizophrenia Patients with Persistent Auditory Hallucinations: A Study on Antisaccade Task Performance.

BACKGROUND: Deficient prefrontal cortex inhibitory control is of particular interest with regard to the pathogenesis of auditory hallucinations (AHs) in schizophrenia. Antisaccade task performance is a sensitive index of prefrontal inhibitory function and has been consistently found to be abnormal in schizophrenia. METHODS: This study investigated the effect of transcranial direct current stimulation (tDCS) on antisaccade performance in 13 schizophrenia patients. RESULTS: The tDCS resulted in significant reduction in antisaccade error percentage (t = 3.4; P = 0.005), final eye position gain (t = 2.3; P = 0.042), and AHs severity (t = 4.1; P = 0.003). CONCLUSION: Our results raise the possibility that improvement in antisaccade performance and severity of AH may be mechanistically related.

Executive dysfunction in first-episode schizophrenia and relationship to duration of untreated psychosis: the West London Study.

BACKGROUND: Many studies have demonstrated early generalised cognitive impairment in schizophrenia. AIMS: To examine executive function in first-episode schizophrenia, characterise the nature of the impairment and specify any relationships with symptoms and duration of untreated psychosis (DUP). METHOD: Patients (n = 136) and normal controls (n = 81) were assessed with the Cambridge Automated Neuropsychological Test Battery, National Adult Reading Test IQ, and Scales for the Assessment of Positive and Negative Symptoms. RESULTS: Memory and executive impairments in patients were independent of IQ level. Spatial working memory was impaired because of inadequate strategy use. On a planning task, patients showed reduced planning times and suboptimal problem-solving. On an attentional set-shifting task, 75% of patients were able to perform an extra-dimensional shift thought to be a core attribute of prefrontal cortex function. Those who failed had significantly longer DUP. CONCLUSIONS: Prefrontal cortex function deteriorates at the onset of psychosis and continues to worsen over time.

Understanding hypnosis metacognitively: rTMS applied to left DLPFC increases hypnotic suggestibility.

INTRODUCTION: According to the cold control theory of hypnosis (Dienes and Perner, 2007), hypnotic response occurs because of inaccurate higher order thoughts of intending. The dorsolateral prefrontal cortex (DLPFC) is a region likely involved in constructing accurate higher order thoughts. Thus, disrupting DLPFC with low frequency repetitive transcranial magnetic stimulation (rTMS) should make it harder to be aware of intending to perform an action. That is, it should be easier to respond to a hypnotic suggestion. METHOD: Twenty-four medium hypnotisable subjects received low frequency rTMS to the left DLPFC and to a control site, the vertex, in counterbalanced order. The hypnotist was blind to which site had been stimulated. Subjects rated how strongly they expected to respond to each suggestion, and gave ratings on a 0-5 scale of the extent to which they experienced the response, for four suggestions (magnetic hands, arm levitation, rigid arm and taste hallucination). The experimenter also rated behavioural response. RESULTS: Low frequency rTMS to the DLPFC rather than vertex increased the degree of combined behavioural and subjective response. Further, subjects did not differ in their expectancy that they would respond in the two conditions, so the rTMS had an effect on hypnotic response above and beyond expectancies. CONCLUSIONS: The results support theories, including cold control theory, postulating a component of hypofrontality in hypnotic response.

The role of the temporal lobe in contextual sentence integration: A single-pulse transcranial magnetic stimulation study.

Neuroimaging studies have shown the left temporal lobe to be important for contextual sentence integration. This study used single-pulse transcranial magnetic stimulation (TMS) to establish stronger causal evidence for the role of this brain region and also explored the involvement of the same cortical region in the right hemisphere (RH). In a semantic decision task, sentences with different cloze probability endings (highly expected, unexpected, and semantically anomalous) were presented to 59 participants. Single-pulse TMS was applied to the left or the right posterior temporal lobe. Vertex stimulation served as a baseline. Left temporal stimulation decelerated responses to expected and unexpected endings in a sentence-integration task. RH stimulation did not affect the responses. These results support the causal role of the left temporal lobe in semantic integration. Single-pulse TMS can contribute to a better understanding of language organization at a sentence level.

Visuo-spatial representations of the alphabet in synaesthetes and non-synaesthetes.

Visuo-spatial representations of the alphabet (so-called 'alphabet forms') may be as common as other types of sequence-space synaesthesia, but little is known about them or the way they relate to implicit spatial associations in the general population. In the first study, we describe the characteristics of a large sample of alphabet forms visualized by synaesthetes. They most often run from left to right and have salient features (e.g., bends, breaks) at particular points in the sequence that correspond to chunks in the 'Alphabet Song' and at the alphabet mid-point. The Alphabet Song chunking suggests that the visuo-spatial characteristics are derived, at least in part, from those of the verbal sequence learned earlier in life. However, these synaesthetes are no faster at locating points in the sequence (e.g., what comes before/after letter X?) than controls. They tend to be more spatially consistent (measured by eye tracking) and letters can act as attentional cues to left/right space in synaesthetes with alphabet forms (measured by saccades), but not in non-synaesthetes. This attentional cueing suggests dissociation between numbers (which reliably act as attentional cues in synaesthetes and non-synaesthetes) and letters (which act as attentional cues in synaesthetes only).

Duration of untreated psychosis and social function: 1-year follow-up study of first-episode schizophrenia.

BACKGROUND: In first-episode schizophrenia, longer duration of untreated psychosis (DUP) predicts poorer outcomes. AIMS: To address whether the relationship between DUP and outcome is a direct causal one or the result of association between symptoms and/or cognitive functioning and social functioning at the same time point. METHOD: Symptoms, social function and cognitive function were assessed in 98 patients with first-episode schizphrenia at presentation and 1 year later. RESULTS: There was no significant clinical difference between participants with short and long DUP at presentation. Linear regression analyses revealed that longer DUP significantly predicted more severe positive and negative symptoms and poorer social function at 1 year, independent of scores at presentation. Path analyses revealed independent direct relationships between DUP and social function, core negative symptoms and positive symptoms. There was no significant association between DUP and cognition. CONCLUSIONS: Longer DUP predicts poor social function independently of symptoms. The findings underline the importance of taking account of the phenomenological overlap between measures of negative symptoms and social function when investigating the effects of DUP.

Comorbid substance use and age at onset of schizophrenia.

BACKGROUND: Substance use may be a risk factor for the onset of schizophrenia. AIMS: To examine the association between substance use and age at onset in substance use and age at onset in a UK, inner-city sample of people with recent-onset schizophrenia. METHOD: The study sample consisted of 152 people recruited to the West London First-Episode Schizophrenia Study. Self-reported data on drug and alcohol use, as well as information on age at onset of psychosis, were collected. Mental state, cognition (IQ, memory and executive function) and social function were also assessed. RESULTS: In total, 60% of the participants were smokers, 27% reported a history of problems with alcohol use, 35% reported current substance use (not including alcohol), and 68% reported lifetime substance use (cannabis and psychostimulants were most commonly used). Cannabis use and gender had independent effects on age at onset of psychosis, after adjusting for alcohol misuse and use of other drugs. CONCLUSIONS: The strong association between self-reported cannabis use and earlier onset of psychosis provides further evidence that schizophrenia may be precipitated by cannabis use and/or that the early onset of symptoms is a risk factor for cannabis use.

Relationship between insight, cognitive function, social function and symptomatology in schizophrenia: the West London first episode study.

OBJECTIVE: To examine the nature and clinical correlates of insight in first-episode schizophrenia, and how these differ from findings in established schizophrenia. METHOD: Insight (and insight dimensions), clinical symptoms, neurocognitive function and social function were assessed in 94 patients with first-episode schizophrenia or schizophreniform disorder according to DSM-IV criteria. RESULTS: Greater global insight was associated with more severe depression. Poor overall insight was associated significantly with more severe negative and disorganisation symptoms as well as poor working memory, and at a trend level with lower current IQ. Patients with poor insight perceived themselves to have a better level of independent performance at daily living activities. CONCLUSION: In first-episode psychosis, the clinical correlates of poor insight are similar to those reported for established schizophrenia. Those patients with greater insight may be at risk of depression. The complex relationships between insight, positive and negative symptoms, neurocognitive dysfunction and social function may reflect the multidimensional nature of insight.

Risk-taking on tests sensitive to ventromedial prefrontal cortex dysfunction predicts early relapse in alcohol dependency: a pilot study.

Twenty one patients in a residential rehabilitation program fulfilling International Classification of Diseases-10 (ICD) criteria for alcohol dependence syndrome were recruited. On neuropsychological tests, alcohol dependent patients relapsed early if they made choices governed by immediate gain irrespective of later outcome, which is consistent with dysfunctional ventromedial-prefrontal cortex mediating the inability to resist the impulse to drink despite ultimately deleterious effects. The authors suggest that the use of neuropsychological tasks of decision making may have several advantages over more conventional strategies for studying alcoholism.