Attentional control parameters following parietal-lobe damage: evidence from normal subjects

Attentional control involves the factors, or cognitive parameters, that determine which environmental inputs receive attention and which do not. Cognitive studies of attentional control have highlighted two general classes of control parameters, bottom-up (data driven or exogenous) parameters and top-down (goal driven or endogenous) parameters. Which of these control parameters is affected following parietal-lobe damage? In parietal-damaged patients, it is possible that a disorder in one control parameter (e.g. goal driven) would appear as a disorder in another parameter (e.g. data driven). To investigate the control parameters that might be affected in parietal patients, we simulated neglect in normal participants by disrupting data-driven information processing. When half of a computer monitor was degraded by translucent tracing paper while normal participants performed a cued spatial attention task (Experiment 1), the normal participants showed a pattern of results similar to patients with unilateral parietal-lobe damage--the so-called "disengage deficit." This pattern of results replicated when neutral attentional cues were included in the experiment (Experiment 2). However, the disengage deficit was not simulated in normal participants with predictive central symbolic cues (Experiment 3) or predictive peripheral cues (Experiment 4). Because perceptual degradation influences data-driven attentional control parameters, we suggest that these control parameters may be disrupted following parietal-lobe damage.     

First- and second-order stimulus length selectivity in New World monkey striate cortex

Motion is a powerful cue for figure-ground segregation, allowing the recognition of shapes even if the luminance and texture characteristics of the stimulus and background are matched. In order to investigate the neural processes underlying early stages of the cue-invariant processing of form, we compared the responses of neurons in the striate cortex (V1) of anaesthetized marmosets to two types of moving stimuli: bars defined by differences in luminance, and bars defined solely by the coherent motion of random patterns that matched the texture and temporal modulation of the background. A population of form-cue-invariant (FCI) neurons was identified, which demonstrated similar tuning to the length of contours defined by first- and second-order cues. FCI neurons were relatively common in the supragranular layers (where they corresponded to 28% of the recorded units), but were absent from layer 4. Most had complex receptive fields, which were significantly larger than those of other V1 neurons. The majority of FCI neurons demonstrated end-inhibition in response to long first- and second-order bars, and were strongly direction selective. Thus, even at the level of V1 there are cells whose variations in response level appear to be determined by the shape and motion of the entire second-order object, rather than by its parts (i.e. the individual textural components). These results are compatible with the existence of an output channel from V1 to the ventral stream of extrastriate areas, which already encodes the basic building blocks of the image in an invariant manner.     

Similarity and discrimination in human Pavlovian conditioning

We report three Pavlovian eyelid conditioning experiments with humans, designed to experimentally decide between elemental and configural learning theories. We used two different designs originally proposed by Redhead and Pearce (1995). In Experiments 1 and 2, three stimulus elements, A, B, and C, were presented in all possible combinations. All patterns were reinforced except for pattern ABC (A/B/C+, AB/AC/BC+, ABC-). According to elemental learning theories, response proportions on A/B/C+ trials should be smaller than on AB/AC/BC+ trials, whereas configural learning theory makes the opposite prediction. The results confirmed neither prediction. In Experiment 3, the A/B/C+, AB/AC/BC+, and ABC- trials were interspersed by D/E/F-, DE/DF/EF-, DEF+ trials. Again, neither prediction was confirmed. We suggest a modification of configural learning theory as a possible explanation of our results.     

Dorsal hippocampal lesions impair appetitive classical conditioning to localized cues

Three experiments examined appetitive classical conditioning in rats with small electrolytic lesions of the dorsal hippocampus. In all the experiments, the reinforcer was food delivery and the conditioned response (CR) entry to the food tray; the three experiments differed in the nature of the conditioned stimulus (CS). When this was a small light located inside the food tray, conditioning was impaired in lesioned animals, but when the CS was a general increase in illumination, they learned at the same rate as controls. With a white noise as the CS, learning was significantly faster in lesioned subjects. These data demonstrate that lesions of the dorsal hippocampus can produce impairments in appetitive delay conditioning, but only with certain types of CS. It is suggested that deficits are found with CSs that are localized in space.     

Does the reaction of abstaining smokers to the smell of other people's cigarettes predict relapse?

Aims Recent ex‐smokers report a range of reactions to other people's cigarette smoke. We examined the hypothesis that those who find the smell of smoke pleasant and tempting are more likely to relapse than those who have a neutral or even negative reaction to it. Design A total of 1110 consecutive patients who attended for smoking cessation treatment and achieved at least 1 week of validated abstinence provided weekly ratings of their reactions to other people's cigarette smoke together with routine baseline measures and weekly ratings of withdrawal discomfort [measured on the Mood and Physical Symptom Scale (MPPS)]. Findings Twenty‐three per cent of the sample found the smell of other people's cigarette smoke during their first week of abstinence pleasant, and 54% found it tempting. There was only a modest correlation between the two variables. Finding the smoke pleasant was not related to smoking status in the following week, but finding the smoke tempting predicted relapse. Ratings of temptation were related to the severity of withdrawal discomfort and to dependence. Entering MPPS ratings of urges to smoke in the given week into regression analysis resulted in the general urges to smoke, rather than urges elicited by other people's smoke, becoming a significant predictor of smoking status in the following week. In patients who maintained continuous abstinence throughout 4 weeks of treatment the pleasantness ratings remained stable, while the ratings of temptation steadily decreased. Conclusions In abstaining smokers, the like or dislike of other people's smoke is not related to relapse. The temptation to smoke elicited by other people's smoke is related to outcome, but only as an indicator of a general ‘temptation threshold’. Patients who find other people's smoke tempting can be reassured that this reaction will gradually decrease.     

Abnormal hippocampal structure and function in clinical anxiety and comorbid depression

Given the high prevalence rates of comorbidity of anxiety and depressive disorders, identifying a common neural pathway to both disorders is important not only for better diagnosis and treatment, but also for a more complete conceptualization of each disease. Hippocampal abnormalities have been implicated in anxiety and depression, separately; however, it remains unknown whether these abnormalities are also implicated in their comorbidity. Here we address this question by testing 32 adults with generalized anxiety disorder (15 GAD only and 17 comorbid MDD) and 25 healthy controls (HC) using multimodal MRI (structure, diffusion and functional) and automated hippocampal segmentation. We demonstrate that (i) abnormal microstructure of the CA1 and CA2‐3 is associated with GAD/MDD comorbidity and (ii) decreased anterior hippocampal reactivity in response to repetition of the threat cue is associated with GAD (with or without MDD comorbidity). In addition, mediation‐structural equation modeling (SEM) reveals that our hippocampal and dimensional symptom data are best explained by a model describing a significant influence of abnormal hippocampal microstructure on both anxiety and depression—mediated through its impact on abnormal hippocampal threat processing. Collectively, our findings show a strong association between changes in hippocampal microstructure and threat processing, which together may present a common neural pathway to comorbidity of anxiety and depression. © 2016 Wiley Periodicals, Inc.     

Masked smoking-related images modulate brain activity in smokers

The questions of whether and how indiscriminate drug-related stimuli could influence drug-users are important to our understanding of addictive behavior, but the answers are still inconclusive. In the present preliminary functional magnetic resonance imaging study using a backward masking paradigm, the effect of indiscriminate smoking-related stimuli on 10 smokers and 10 nonsmokers was examined. The BOLD response showed a significant reduction (P = 0.001) in the right amygdala of smokers when they viewed but did not perceive masked smoking-related stimuli, while no significant differences were found in the nonsmoker group. More voxels in anterior cingulate cortex were negatively correlated with the amygdala during the masked smoking-related picture condition in smokers but not in nonsmokers, whereas more positively correlated voxels were observed during the masked neutral condition. The BOLD response in drug-users indicates the amygdala responds to drug-related stimuli that are below the perceptual threshold. The functional connectivity data suggest a functional interaction between the amygdala and the anterior cingulate cortex when drug users view 33 ms back-masked drug-related stimuli. This observation suggests that the amygdala plays an important role in the indiscriminate drug-related cue process.     

Psychophysiological responses to drug-associated stimuli in chronic heavy cannabis use

Due to learning processes originally neutral stimuli become drug-associated and can activate an implicit drug memory, which leads to a conditioned arousing 'drug-seeking' state. This condition is accompanied by specific psychophysiological responses. The goal of the present study was the analysis of changes in cortical and peripheral reactivity to cannabis as well as alcohol-associated pictures compared with emotionally significant drug-unrelated and neutral pictures in long-term heavy cannabis users. Participants were 15 chronic heavy cannabis users and 15 healthy controls. Verbal reports as well as event-related potentials of the electroencephalogram and skin conductance responses were assessed in a cue-reactivity paradigm to determine the psychophysiological effects caused by drug-related visual stimulus material. The evaluation of self-reported craving and emotional processing showed that cannabis stimuli were perceived as more arousing and pleasant and elicited significantly more cannabis craving in cannabis users than in healthy controls. Cannabis users also demonstrated higher cannabis stimulus-induced arousal, as indicated by significantly increased skin conductance and a larger late positivity of the visual event-related brain potential. These findings support the assumption that drug-associated stimuli acquire increased incentive salience in addiction history and induce conditioned physiological patterns, which lead to craving and potentially to drug intake. The potency of visual drug-associated cues to capture attention and to activate drug-specific memory traces and accompanying physiological symptoms embedded in a cycle of abstinence and relapse – even in a 'so-called' soft drug – was assessed for the first time.     

Effects of handwriting exercise on functional outcome in Parkinson disease: A randomized controlled trial

Parkinson disease (PD) patients frequently experience micrographia and difficulty writing, which could potentially impact their quality of life. This study aimed to determine whether handwriting exercise could improve fine manual motor function in PD. The study was a randomized controlled trial assessing the efficacy of a 4-week handwriting exercise using a newly developed handwriting practice book. The primary endpoint was an improvement in the time used to complete the handwriting test. Secondary endpoints were accuracy of the writing performance, patient’s subjective rating scale of their handwriting and a UPDRS part III motor examination. Of a total of 46 subjects, 23 were randomly assigned to the handwriting exercise group. After 4 weeks, the mean time used to complete the test was significantly lower in the exercise group, compared to the control group (143.43 ± 34.02 vs. 175 ± 48.88 s, p = 0.015). Mean time used to complete the handwriting test decreased from the baseline by 16.16% in the exercise group, but increased by 3.63% in the control group (p < 0.001). Significant improvements were also observed by assessing the subjective rating scale and the UPDRS part III scores. The 4-week handwriting exercise using the studied handwriting practice book appears to promote an improvement in writing speed and motor function of hands. The optimal duration and frequency of the exercise, the quantity and characteristic of the letters in the handwriting practice book, and the benefits of the exercise in other languages merit further studies.