[An unrecognized cause of dyspnoea]. / Een miskende oorzaak van dyspneu.

BACKGROUND: Neuralgic amyotrophy is characterised by pain in the neck or shoulder region, followed by neuropathy of both motor and sensory nerves of the brachial plexus. The incidence of this condition is estimated at 1/1000 per year. In a rare variant of the syndrome, involvement of both phrenic nerves can occur, leading to diaphragmatic paralysis and severe orthopnoea. CASE DESCRIPTION: A 67-year-old woman was referred to us with acute orthopnoea. Imaging studies showed bilateral diaphragmatic paralysis, and electromyography (EMG) confirmed neuropathy of both phrenic nerves. The diagnosis was bilateral neuralgic amyotrophy. The patient received nocturnal ventilation support via nasal high flow oxygen therapy. This symptomatic treatment had a positive effect. CONCLUSION: Isolated phrenic nerve neuropathy is a rare variant of neuralgic amyotrophy, leading to orthopnoea. Recovery is slow and frequently incomplete. Supportive treatment with non-invasive ventilation support is necessary to improve the patient's quality of life.

Oxytocin enhances orienting to social information in a selective group of high-functioning male adults with autism spectrum disorder.

OBJECTIVE: The study investigated the effects of nasally administered oxytocin on neurophysiological orienting to empathy-evoking pictures in normally intelligent male adults with and without an autism spectrum disorder (ASD). It further investigated whether these effects might be moderated by the individual's approach and avoidance tendencies. METHODS: All subjects participated in a randomised double-blind placebo controlled crossover trial where either oxytocin (OXT) or placebo was administered preceding the viewing of affective pictures.The pictures, selected from the International Affective Picture System (IAPS), represented a systematic variation of pleasant, unpleasant and neutral scenes with and without humans. Both cardiac (ECR) and cortical (LPP) evoked orienting responses were measured and both were enhanced for the pictures with humans, in particular for the unpleasant ones. RESULTS: No significant group differences were found, nor were there any treatment effects. Moderator analysis, however, demonstrated that OXT did enhance orienting to affective pictures with humansin male adults with ASD who are easily distressed when seeing others in stressful situations and in healthy males who are highly sensitive to anticipated punishment and criticism or have a low drive for goal achievement. CONCLUSION: Individual differences in stress-related avoidance tendencies should be taken into account when considering OXT as a treatment of social deficiencies in autism.

Severity of depression and anxiety are predictors of response to antidepressant treatment in Parkinson's disease.

BACKGROUND: Antidepressants have appeared to be more effective than placebo treatment in treating depressive syndromes in patients with Parkinson's disease (PD). OBJECTIVE: To identify factors that predict improvement in depressive symptoms during antidepressant treatment in depressed PD patients. METHODS: A secondary analysis was performed on the dataset of the Randomized Placebo-controlled Study of Antidepressants in PD (SAD-PD), in which 76 patients received active treatment with either paroxetine or venlafaxine extended release (XR), and 39 patients received placebo treatment. Backward stepwise regression analyses were conducted with change in 24-item Hamilton Depression Rating Scale (HAMD-24) score between assessments at baseline and week 12 as the main outcome measure, and sex, age, baseline HAMD-24 score, Unified Parkinson's Disease Rating Scale section III (UPDRS-III) score, Mini-Mental State Examination (MMSE), and the Clinical Anxiety Scale (CAS) as independent variables. RESULTS: In both the active treatment and placebo groups, higher baseline HAMD-24 score and lower UPDRS-III score were associated with greater reduction in HAMD-24 score. Higher anxiety scores predicted less response in the active treatment group. Higher MMSE scores predicted greater response only in the placebo-treated group. Sex and age were no predictors of response. CONCLUSIONS: Higher pre-treatment depression scores and lower pre-treatment anxiety scores are the two most important predictors for improvement during antidepressant treatment in depressed PD patients, which is in line with those found in treatment studies of depressed non-PD patients. Furthermore, our results indicate the requirement for different or more intensive treatment for depressed PD patients with more severe anxiety symptoms.

Are there sex differences in ERPs related to processing empathy-evoking pictures?

OBJECTIVE: This study aimed to investigate sex differences in the temporal dynamics of experiencing empathy by using electrophysiological measurements. METHODS: Twenty-five females and 27 males viewed 414 pictures of the International affective picture system varying in emotional valence (positive, negative and neutral) and presence of humans (human and scenes). EEG event related potentials (ERPs) were obtained and correlations were computed with self-reported empathy. RESULTS: Compared to males, females showed increased anterior N2 and parietal LPP amplitudes to humans contrasted with scenes (independent of emotional valence) and to negative contrasted with neutral emotions (independent of human presence). Independent of sex the N1 and anterior N2 were specifically increased for positive human emotions and the parietal LPP for negative human emotions. Across sexes, the N2 and LPP human emotion effects and LPP human effects were associated with self-reported affective empathy, but not with cognitive empathy. CONCLUSIONS: This study provides electrophysiological evidence that women prioritize the processing of socially relevant and negative emotional information, but that women did not show enhanced brain potentials to pictures with positive or negative emotions in humans.

Free recall of pleasant words from recency positions is especially sensitive to acute administration of cortisol.

In a recent study we investigated the acute effects of cortisol administration in healthy male volunteers on free recall of pleasant, unpleasant, and neutral nouns using a between-subjects double-blind placebo-controlled design. The volunteers were administered 10 mg of hydrocortisone or placebo between 9:00 and 10:30. Two hours after administration of cortisol a decline in recall of neutral and pleasant words was found, while recall of unpleasant words did not change. These results are consistent with a possible inhibitory influence of cortisol on a prefrontal dopaminergic mechanism involved in approach and positivity bias. In this paper we first explain why this interpretation would predict recall of pleasant words from recency positions to be especially sensitive to cortisol administration. Comparing primacy and recency recall of pleasant and unpleasant words, there proved to be a selective decline in recall of pleasant recency words. These results did not appear to stem from differences in recall strategies between our groups of volunteers.

Inhibition, response mode, and stimulus probability: a comparative event-related potential study.

OBJECTIVES: In the present study, effects of response mode (finger movement or counting) and stimulus probability on inhibitory processes were studied. METHODS: Electroencephalographic activity was registered in a visual go/nogo paradigm. Subjects either responded manually to go stimuli or counted silently the occurrence of each go stimulus in different conditions. In both response mode conditions, response probability was varied. RESULTS: For finger movement and counting, similar N2 and P3 go/nogo effects were found. The amplitude of the nogo N2 and nogo P3 varied as a negative function of nogo stimulus probability. The go P3 varied as a negative function of go stimulus probability. In the manual condition, however, the descending flank of the go N2 at anterior electrode sites was more negative in the 0.50go and 0.75go probability trials than in the 0.25go probability trials. CONCLUSIONS: The results of the present study confirm the hypothesis that differences between go and nogo event-related potentials are not dependent on overt movement-related potentials. It could be speculated that the probability effect on the N2 amplitude in go trials in the manual condition has to be explained in terms of a modulation of the strength of motoric preparation processes varying as a positive function of the probability of the go stimulus.

Selective attention to a facial feature with and without facial context: an ERP-study.

The present experiment addressed the question whether selectively attending to a facial feature (mouth shape) would benefit from the presence of a correct facial context. Subjects attended selectively to one of two possible mouth shapes belonging to photographs of a face with a happy or sad expression, respectively. These mouths were presented randomly either in isolation, embedded in the original photos, or in an exchanged facial context. The ERP effect of attending mouth shape was a lateral posterior negativity, anterior positivity with an onset latency of 160-200 ms; this effect was completely unaffected by the type of facial context. When the mouth shape and the facial context conflicted, this resulted in a medial parieto-occipital positivity with an onset latency of 180 ms, independent of the relevance of the mouth shape. Finally, there was a late (onset at approx. 400 ms) expression (happy vs. sad) effect, which was strongly lateralized to the right posterior hemisphere and was most prominent for attended stimuli in the correct facial context. For the isolated mouth stimuli, a similarly distributed expression effect was observed at an earlier latency range (180-240 ms). These data suggest the existence of separate, independent and neuroanatomically segregated processors engaged in the selective processing of facial features and the detection of contextual congruence and emotional expression of face stimuli. The data do not support that early selective attention processes benefit from top-down constraints provided by the correct facial context.

Response priming in a go/nogo task: do we have to explain the go/nogo N2 effect in terms of response activation instead of inhibition?

OBJECTIVES: In the present study, we examined the effects of response priming on the event-related potentials (ERPs) evoked by target stimuli in a go/nogo task. METHODS: In each trial, subjects were presented a cue and a target stimulus. The cue informed subjects about the following target in that trial, and therefore, also about the kind of response (right-hand response, left-hand response, no overt response) potentially to be given in that trial. RESULTS: The traditional N2 and P3 go/nogo effects were replicated: the ERPs to nogo targets were negative compared to the ERPs evoked by go targets in the N2 latency range at frontal electrode sites, and the nogo P3s were more anteriorly distributed than the go P3s. Comparing the ERPs evoked by nogo targets, we found the P3, but not the N2, to be modulated by response priming. CONCLUSIONS: These results seem to indicate that the P3, but not the N2, is associated with response inhibition, or with an evaluation/decision process with regard to the expected and/or given response. It could be speculated that the traditional go/nogo N2 effect has to be explained in terms of response activation instead of response inhibition.

Working memory processes show different degrees of lateralization: evidence from event-related potentials.

This study aimed to identify different processes in working memory, using event-related potentials (ERPs) and response times. Abstract polygons were presented for memorization and subsequent recall in a delayed matching-to-sample paradigm. Two polygons were presented bilaterally for memorization and a cue indicated whether one (and if so, which one of the two) or both polygons had to be memorized. A subsequent test figure was presented unilaterally to the left or right visual field and had to be compared with the memorized figure(s). ERP results suggested that memorization takes place in a visual buffer in contralateral posterior brain areas, whereas identification of the test stimulus as a target appears to be mainly a left hemispheric process. Increased response times were found for nontarget test stimuli as compared to targets, and for target test stimuli that were presented contralaterally with respect to the location of the memorized stimulus. In addition, response times were slower when two figures were memorized than when only one was memorized.

Implicit sub-unit learning in a serial reaction time task in humans.

In the present serial reaction time task experiment (SRT), a fixed 12-item sequence was practiced in order to evaluate the effect on response times to 3-item sub sequences (triplets) in a subsequent random sequence. Subjects were visually cued to press one out of four keys with a corresponding right-hand finger. The occurrence of implicit sequence knowledge was evidenced by the increase in mean response time when the transition was made from the final 12-item sequence block to the subsequent random block. In the stimulus-set applied, a total of 36 triplets could be constructed, of which 24 triplets were encountered only during the random blocks (random-only triplet set) (RO-set), whereas 12 triplets were also part of the sequence used in the sequence blocks (sequence-also triplet set) (SA-set). Approximately 35% of the triplets that comprised the two random blocks were also presented in the sequence blocks. There was no difference in mean response times between the triplet sets in the random block that preceded the sequence blocks. In the final random block, however, the SA-set induced significantly faster responses as compared with the RO-set. We argue that stimulus response associations within the SA-set are responsible for the difference in response times between the two triplet sets in the final random block.

Visual semantic features are activated during the processing of concrete words: event-related potential evidence for perceptual semantic priming.

There has been conflicting evidence to date regarding the existence of non-strategic semantic priming based on semantic similarity, and in particular on visual-perceptual semantic features (e.g., button-coin: words refer to objects with the same global shape). Both event-related potential (ERP) and reaction time (RT) measures were employed to investigate visual-perceptual semantic priming in a word-pair lexical decision task designed to minimise the contribution of conscious strategic processing. While no RT priming effect was observed, a robust priming effect was obtained on the N400 component of the ERP. This result shows that semantic priming, as indexed by the N400 component, can be supported by nonassociative visual-perceptual semantic relations. The data are consistent with perceptual form information being accessed during the processing of concrete words, and provide support for models of semantic representation which incorporate semantic features and form information.

Sentence comprehension and word repetition: a positron emission tomography investigation.

Using positron emission tomography, visual presentation of sentences was shown to cause increased regional cerebral blood flow relative to word lists in the left lateral anterior superior and middle temporal gyri, attributable to cognitive processes that occur during sentence comprehension in addition to those carried out during word comprehension. Additional comparisons showed that repeating words (in a different context, when subjects did not attempt to learn the initial lists) led to significant patterns of both increased blood flow (left putamen and right caudate) and decreased blood flow (left posterior temporal lobe). Increases are argued to reflect retrieval of memory traces, whereas decreases reflect diminished necessity for processing of input. A decrease in the left inferior parietal lobe was attributable to other factors.

ERP effects of spatial attention and display search with unilateral and bilateral stimulus displays.

Two experiments were performed in which the effects of selective spatial attention on the ERPs elicited by unilateral and bilateral stimulus arrays were compared. In Experiment 1, subjects received a series of grating patterns. In the unilateral condition these gratings were presented one at a time, randomly to the right or left of fixation. In the bilateral condition, gratings were presented in pairs, one to each side of fixation. In the unilateral condition standard ERP effects of visual spatial attention were observed. However, in the bilateral condition we failed to observe an attention related posterior contralateral positivity (overlapping the P1 and N1 components, latency interval about 100-250 ms), as reported in several previous studies. In Experiment 2, we investigated whether attention related ERP lateralizations are affected by the task requirement to search among multiple objects in the visual field. We employed a task paradigm identical to that used by Luck et al. (Luck, S.J., Heinze, H.J., Mangun, G.R., Hillyard, S.A., 1990. Visual event-related potentials index focused attention within bilateral stimulus arrays. II. Functional dissociation of P1 and N1 components. Electroencephalogr. Clin. Neurophysiol. 75, 528-542). Four letters were presented to a visual hemifield, simultaneously to both the attended and unattended hemifields in the bilateral conditions, and to one hemifield only in the unilateral conditions. In a focused attention condition, subjects searched for a target letter at a fixed position, whereas they searched for the target letter among all four letters in the divided attention condition (as in the experiment of Luck et al., 1990). In the bilateral focused attention condition, only the contralateral P1 was enhanced. In the bilateral divided attention condition a prolonged posterior positivity was observed over the hemisphere contralateral to the attended hemifield, comparable to the results of Luck et al. (1990). A comparison of the ERPs elicited in the focused and divided attention conditions revealed a prolonged 'search related negativity'. We discuss possible interactions between this negativity and attention related lateralizations. The display search negativity consisted of two phases, one phase comprised a midline occipital negativity, developing first over the ipsilateral scalp, while the second phase involved two symmetrical occipitotemporal negativities, strongly resembling the N1 in their topography. The display search effect could be modelled with a dipole in a medial occipital (possibly striate) region and two symmetrical dipoles in occipitotemporal brain areas. We hypothesize that this effect reflects a process of rechecking the decaying information of iconic memory in the occipitotemporal object recognition pathway.

An event-related brain potential correlate of visual short-term memory.

Event-related potentials (ERPs) were recorded as 12 subjects performed a delayed matching to sample task. We presented two bilateral abstract shapes and cued spatially which had to be memorized for a subsequent matching task: left, right or both. During memorization a posterior slow negative ERP wave developed over the hemisphere contralateral to the memorized shape. This effect was similar in high and low memory load trials while the memory figures were visible (for 1000 ms). As the figures disappeared (for 1500 ms), the effect persisted only in the low memory load conditions. We suggest that the contralateral negativity reflects a visual short-term memory process and that capacity limitation in the high memory load condition causes this process to collapse.

Localizing components of a complex task: sentence processing and working memory.

Three areas of the left hemisphere play different roles in sentence comprehension. An area of posterior middle and superior temporal gyrus shows activation correlated with the structural complexity of a sentence, suggesting that this area supports processing of sentence structure. The lateral anterior temporal gyrus is more activated bilaterally by all sentence conditions than by word lists; thus the function of the area probably does not directly support processing of structure but rather processing of words specific to a sentence context. Left inferior frontal cortex also shows activation related to sentence complexity but is also more activated in word list processing than in simple sentences; this region may thus support a form of verbal working memory which maintains sentence structural information as well as lexical items.

Color selection and location selection in ERPs: differences, similarities and 'neural specificity'.

It was hypothesized that color selection consists of two stages. The first stage represents a feature specific selection in neural populations specialized in processing color. The second stage constitutes feature non-specific selections, related to executive attentional processes and/or motor processes. This hypothesis was tested by investigating the effects of selectively attending to a specific color, location, or conjunction of location and color on the ERPs elicited by briefly flashed gratings. The gratings differed on three dimensions: color (red or blue), location in the visual field (4.4 degrees to the left or right of fixation) and form (target or non-target). Subjects had to respond to the presentation of target gratings in the attended category. Color selection was reflected in an enhanced parietal positivity in the 150-190 ms interval. Source analyses suggested that this color selection positivity might be generated in the basal occipital cortex, possibly human V4, an area of the brain specialized in color processing. The effect was separated from the P1 spatial attention effect both in topography and sources. Color selection was also reflected in a contralateral occipitotemporal negativity, which resembled the N1 spatial attention effect both in timing and topography. And finally, color selection was reflected in an N2b component. This N2b was similar in timing, topography and sources to the N2b's elicited by location selection and conjunction selection. We suggested that the N2b reflects feature non-specific selection processes, elicited by a range of attended stimuli, and possibly reflects activity in the anterior cingulate cortex. The NP80 was unaffected by attention to color and/or location and localized in striate cortex.

An ERP study of visual spatial attention and letter target detection for isoluminant and nonisoluminant stimuli.

The event-related potential (ERP) effects of visual spatial attention and letter target detection for stimuli presented against a (nonisoluminant) dark background or against an isoluminant grey background were investigated. The goal was to study how the perceptual variable of luminance would influence early ERP reflections of selective attention. Such effects could further substantiate the claim that selective attention operates at the level of early perceptual processing and could provide evidence regarding the role of different visual routes in selective attention. Isoluminance increased the peak latency of the early ERP deflections (NP80, P1, and N1) by 40-50 ms. The ERP effects of spatial attention, consisting of P1 and N1 amplitude enhancements, were similarly delayed by isoluminance, supporting the idea that early selective processing is strongly dependent on bottom-up perceptual processing. P300 latency and reaction time were delayed by 70-75 ms, the additional delay probably reflecting that isoluminance affected decision processes in addition to perceptual processes. Isoluminance left the scalp topographies of the early ERP deflections largely unaffected, although a slight shift of the N1 topography in the isoluminant condition toward more inferior lateral posterior regions of the scalp could have reflected an increased contribution from ventral (occipitotemporal) brain areas. Relative to nontarget letters, targets presented at both attended and unattended spatial positions elicited an early contralaterally dominant lateral occipitotemporal negativity (N2pc). This ERP component is proposed to reflect an early, partly automatic process of template matching, consistent with indications from spatiotemporal dipole modelling that the N2pc was generated in inferior occipitotemporal brain regions.

The role of neuroimaging in the discovery of processing stages. A review.

In this contribution we show how neuroimaging methods can augment behavioural methods to discover processing stages. Event Related Brain Potentials (ERPs), Brain Electrical Source Analysis (BESA) and regional changes in cerebral blood flow (rCBF) do not necessarily require behavioural responses. With the aid of rCBF we are able to discover several cortical and subcortical brain systems (processors) active in selective attention and memory search tasks. BESA describes cortical activity with high temporal resolution in terms of a limited number of neural generators within these brain systems. The combination of behavioural methods and neuroimaging provides a picture of the functional architecture of the brain. The review is organized around three processors: the Visual, Cognitive and Manual Motor Processors.