Do neck-proprioceptive and caloric-vestibular stimulation influence covert visual attention in normals, as they influence visual neglect?

Neck-proprioceptive and caloric-vestibular stimulation have been shown to ameliorate the spatial bias exhibited by patients suffering from unilateral visual neglect. These interventions might in principle have their effect by biasing covert attention towards the neglected side. If so, the same interventions should also modulate covert attention in neurologically-intact subjects. However, we demonstrate here that neither neck-proprioception (vibration of left neck muscles) nor caloric-vestibular stimulation (injection of iced water into the left ear) affect covert visual attention in healthy individuals. These results from normals may distinguish between different accounts for unilateral neglect in patients. In particular, they argue against explanations of neglect solely in terms of a pathological misperception of body orientation within an otherwise normal neural representation of space.     

What kind of visual spatial attention is impaired in neglect?

The distribution of spatial attention across the horizontal meridian of the visual field, as assessed by a simple reaction time (RT) paradigm, is dramatically abnormal in neglect patients. In the contralesional hemifield, RT increases sharply from centre to periphery, while in the ipsilesional hemifield, it decreases paradoxically from centre to mid-periphery. In the present study, we firstly asked whether this abnormal distribution of spatial attention is still present when patients know in advance the location of the impending stimulus, and second whether and to which extent it may be influenced by the concomitant presence of hemianopia. In Experiment 1, the stimuli were presented either predictably (blocks of same-point presentations) or unpredictably (blocks of randomised presentations) to one of several contralesional and ipsilesional field locations. As was the case for control subjects, neglect patients showed an overall RT decrease with same-point presentations. However, their abnormal contralesional RT lengthening and ipsilesional speeding were still present. In Experiment 2, the trials were blocked to same-hemifield presentations. In the ipsilesional field condition, neglect patients with and without hemianopia showed the same distorted distribution of attention favouring mid-periphery over central field locations. Two conclusions can be drawn from these experiments: first, the bulk of the abnormal deployment of spatial attention in neglect patients is related to an impairment of exogenous attention which cannot be compensated for by a spared endogenous control. Second, hemianopia does not affect the paradoxical speeding up of RT typically found in the mid-periphery of the ipsilesional field of neglect patients.     

A common basis for visual and tactile exploration deficits in spatial neglect?

One of the fundamental characteristics of spatial neglect is an imbalanced visual search behaviour favouring stimuli on the right side of space while largely ignoring those on the left side. Opinions differ as to whether this reflects a general orientational bias caused by impaired supramodal body-centred reference systems, or a modality-specific search disorder. A prediction of the former model would be that exploratory activity is similarly impaired both in vision and in the absence of visual control. We addressed this hypothesis by comparing patients' visual and tactile search in the same workspace. Our results show that the centre of exploration activity in both modalities was substantially shifted towards the ipsilesional right side in the neglect group as compared to healthy and patient controls. This bias was more accentuated for visual search. We found a clear linear relationship between the visual and tactile search biases in the patient group with spatial neglect. Our finding suggests that the critical component guiding search behaviour in neglect, whether visually or tactually, is a general rightward orientation bias. In addition, we observed an increased repetition rate in both modalities which affected the whole workspace. This implies that the apparent spatial working memory deficit dissociates from the mechanisms inducing the orientation bias.     

Impaired spatial working memory: one component of the visual neglect syndrome?

Both impaired spatial working memory (SWM) and unilateral neglect may follow damage to the right parietal lobe. We propose that impaired SWM can exacerbate visual neglect, due to failures in remembering locations that have already been searched. When combined with an attentional bias to the ipsilesional right side, such a SWM impairment should induce recursive search of ipsilesional locations. Here we studied a left neglect patient with a right temporoparietal haemorrhage. On a nonlateralised, purely vertical SWM task, he was impaired in retaining spatial locations.

In a visual search task, his eye position was monitored while his spatial memory was probed. He recursively searched through right stimuli, re-fixating previously inspected items, and critically treated them as if they were new discoveries, consistent with the SWM deficit. When his recovery was tracked over several months, his SWM deficit and left neglect showed concurrent improvements. We argue that impaired SWM may be one important component of the visual neglect syndrome.     

Could visual neglect induce amblyopia?

Oculomotor nerve disease is a common cause of diplopia. When strabismus is present, absence of diplopia has to induce the research of either uncovering of visual fields or monocular suppression, amblyopia or blindness. We describe the case of a 41-year-old woman presenting with right oculomotor paresis and left object-centred visual neglect due to a right fronto-parietal haemorrhage expanding to the right peri-mesencephalic cisterna caused by the rupture of a right middle cerebral artery aneurysm. She never complained of diplopia despite binocular vision and progressive recovery of strabismus, excluding uncovering of visual fields. Since all other causes were excluded in this case, we hypothesise that the absence of diplopia was due to the object-centred visual neglect. Partial internal right oculomotor paresis causes an ocular deviation in abduction; the image being perceived deviated contralaterally to the left. Thus, in our case, the neglect of the left image is equivalent to a right monocular functional blindness. However, bell cancellation test clearly worsened when assessed in left monocular vision confirming that eye patching can worsen attentional visual neglect. In conclusion, our case argues for the possibility of a functional monocular blindness induced by visual neglect. We think that in presence of strabismus, absence of diplopia should induce the search for hemispatial visual neglect when supratentorial lesions are suspected.     

Is there a role of visual cortex in spatial hearing?

The integration of auditory and visual spatial information is an important prerequisite for accurate orientation in the environment. However, while visual spatial information is based on retinal coordinates, the auditory system receives information on sound location in relation to the head. Thus, any deviation of the eyes from a central position results in a divergence between the retinal visual and the head-centred auditory coordinates. It has been suggested that this divergence is compensated for by a neural coordinate transformation, using a signal of eye-in-head position. Using functional magnetic resonance imaging, we investigated which cortical areas of the human brain participate in such auditory-visual coordinate transformations. Sounds were produced with different interaural level differences, leading to left, right or central intracranial percepts, while subjects directed their gaze to visual targets presented to the left, to the right or straight ahead. When gaze was to the left or right, we found the primary visual cortex (V1/V2) activated in both hemispheres. The occipital activation did not occur with sound lateralization per se, but was found exclusively in combination with eccentric eye positions. This result suggests a relation of neural processing in the visual cortex and the transformation of auditory spatial coordinates responsible for maintaining the perceptual alignment of audition and vision with changes in gaze direction.     

Do birds possess homologues of mammalian primary visual, somatosensory and motor cortices?

Recent data on the expression of several homeobox genes in the embryonic telencephalon of mammals, birds and reptiles support the homology of a part of the avian pallium, named the Wulst, and at least the more-medial and superior parts of mammalian neocortex. This conclusion is also supported by previous embryological, topological and hodological data. Furthermore, new evidence on the connections and electrophysiological properties of specific subfields within the avian Wulst, and on the thalamic territories that project to these fields, supports the more-specific conclusion that a primary visual area and a primary somatosensory-somatomotor area are present in the avian Wulst; these areas are likely to be homologous to their counterparts in mammals. In spite of this, developmental, morphological and comparative evidence indicate that some structural and physiological traits that appear to be similar in the Wulst and neocortex (such as the lamination or binocularity) evolved independently in birds and mammals.     

Do parental psychopathology and unfavorable family environment predict the persistence of social phobia?

Parental psychopathology and unfavorable family environment are established risk factors for onset of offspring social phobia (SP), but their associations with the further course, e.g., persistence of the disorder, remain understudied. A community cohort of 1395 adolescents and their parents was followed-up over almost 10 years using the DIA-X/M-CIDI. Parental diagnostic interviews were supplemented by family history data. Parental rearing was retrospectively assessed by the Questionnaire of Recalled Parental Rearing Behavior in offspring, and family functioning by the Family Assessment Device in parents. Persistence measures (proportion of years affected since onset) were derived from diagnostic interviews, using age of onset, age of recency, and course information. Lack of emotional warmth and dysfunctional family functioning characteristics were associated with higher SP persistence, particularly in interaction with parental psychopathology. Predictors for SP persistence differ from those predicting SP onset. Unfavorable family environment alone and in interaction with parental disorders predict higher SP persistence.     

Where is the "straight ahead" in spatial neglect?

We investigated the subjective straight-ahead (SSA) projection of body-midline parts (head and trunk) in patients with neglect and patients with nonneglect, using a method disentangling lateral shift and lateral tilt components of the bias. Patients with neglect showed a similar counterclockwise SSA tilt for each body part and an ipsilesional lateral shift, more severe for the trunk than for the head. Thus, neglect results in a tilt of the body midline representation.     

Is the visual analyzer orthographic-specific? Reading words and numbers in letter position dyslexia

Letter position dyslexia (LPD) is a deficit in the encoding of letter position within words. It is characterized by errors of letter migration within words, such as reading trail as trial and form as from. In order to examine whether LPD is domain-specific, and to assess the domain-specificity of the visual analysis system, this study explored whether LPD extends to number reading, by testing whether individuals who have letter migrations in word reading also show migrations while reading numbers. The reading of words and numbers of 12 Hebrew-speaking individuals with developmental LPD was assessed. Experiment 1 tested reading aloud of words and numbers, and Experiment 2 tested same-different decisions in words and numbers. The findings indicated that whereas the participants with developmental LPD showed a large number of migration errors in reading words, 10 of them read numbers well, without migration errors, and not differently from the control participants. A closer inspection of the pattern of errors in words and numbers of two individuals who had migrations in both numbers and words showed qualitative differences in the characteristics of migration errors in the two types of stimuli. In word reading, migration errors appeared predominantly in middle letters, whereas the errors in numbers occurred mainly in final (rightmost) digits. Migrations in numbers occurred almost exclusively in adjacent digits, but in words migrations occurred both in adjacent and in nonadjacent letters. The results thus indicate that words can be selectively impaired, without a parallel impairment in numbers, and that even when numbers are also impaired they show different error pattern. Thus, the visual analyzer is actually an orthographic visual analyzer, a module that is domain-specific for the analysis of words.     

Do adverse life events and mood disorders influence delayed presentation of breast cancer?

OBJECTIVE: The purpose of this study is to examine the influence of adverse life experiences and mood disorders on delayed presentation of breast cancer. METHODS: One hundred fifty-eight patients were interviewed 5 months after diagnosis to assess the prevalence of adverse life events and difficulties using the Bedford College Life Events and Difficulties Schedule, and psychiatric morbidity using the Structured Clinical Interview (SCID) and DSM-III-R diagnostic criteria. RESULTS: There was no association between experiencing a severe life event (p = 0.5) or difficulty, whether severe or nonsevere (p = 0.8), in the year preceding symptom discovery and patient delay. Counterintuitively, women who presented promptly to their GP (<12 weeks) with breast symptoms were more likely than those who delayed >/=12 weeks to report having a nonsevere event in the year before symptom discovery (p < 0.001). This appeared however, to be an artifact, because the women presenting promptly were recalling events that were closer in time to the research interview. Patient delay was not related to prevalence of depression (p = 0.2) or anxiety (p = 0.8) in the year preceding symptom discovery. CONCLUSION: This study suggests that neither adverse life experiences nor mood disorder in the year before symptom discovery increase the risk of patients with symptoms of breast cancer delaying their presentation to a general practitioner.     

Symmetrical hemispheric priming in spatial neglect: A hyperactive left-hemisphere phenomenon?

Hemispheric rivalry models of spatial neglect suggest that the left hemisphere becomes hyperactive following right-hemisphere lesions since the two hemispheres normally exert an inhibitory influence on each other via callosal connections. Using a masked hemifield priming paradigm, we investigated whether the putative change in hemispheric balance involves other, higher-order abstract representational systems in spatial neglect. Participants consisted of 12 neglect patients with right-hemisphere damage and three groups of control participants, i.e., 12 young healthy controls, 10 age-matched healthy controls and 10 right-hemisphere patients without spatial neglect. In each trial, participants made semantic categorization about a centrally presented target word which was preceded by a masked prime flashed either to the left or right visual field. All three control groups exhibited strong left-hemisphere advantage in inhibitory syllabic priming, consistent with the known left-hemisphere dominance in lexical inhibition during reading. By contrast, neglect patients exhibited a symmetrical pattern of priming between the left and right visual fields. These results suggest that (1) the neglected hemifield can rapidly extract abstract information even from weak and normally non-perceptible visual stimuli, but that (2) the normal left hemispheric dominance in reading is absent in neglect patients probably because of the generalized hyperactivity of the left hemisphere. Our results demonstrate a covert behavioral change in spatial neglect which may reflect the altered inter-hemispheric balance in the bilateral word recognition system encompassing lexico-semantic memory.