焦虑情绪对海洛因依赖者注意定向的影响

目的研究海洛因依赖者特质焦虑与状态焦虑对其注意定向过程的影响。方法通过状态焦虑量表以及特质焦虑量表评估40例海洛因依赖者(男36例,女4例)和40名对照者(男36名,女4名)的状态焦虑和特质焦虑,并采用线索—目标范式评估被试者注意定向中的直接定向与解离/重新定向过程。结果海洛因依赖组的状态焦虑[(42.65±6.58)vs.(36.60±8.91)]和特质焦虑[(44.43±7.67)vs.(37.00±8.63)]评分高于对照组,差异有统计学意义(P0.05)。相关分析示,海洛因依赖者的状态焦虑(r=-0.259,P=0.020)、特质焦虑(r=-0.248,P=0.026)分别与直接定向反应时差值呈负相关,并与解离/重新定向反应时差值呈正相关[状态焦虑(r=0.333,P=0.003);特质焦虑(r=0.356,P=0.001)]。结论海洛因依赖者具有较严重的焦虑情绪,状态/特质焦虑可能与海洛因依赖者的直接定向过程以及解离/重新定向过程有关。     

Hemispheric differences in attentional orienting by social cues

Research points to a right hemisphere bias for processing social stimuli. Hemispheric specialization for attention shifts cued by social stimuli, however, has been rarely studied. We examined the capacity of each hemisphere to orient attention in response to social and nonsocial cues using a lateralized spatial cueing paradigm. We compared the up/down orienting effects of eye gaze cues, arrow cues, and peripheral cues (change in luminance). Results revealed similar cueing effects in each visual field for nonsocial cues, but asymmetric effects for social cues. At both short (150 ms) and long (950 ms) cue-target intervals, gaze cueing was significant in the LVF, but not in the RVF. Thus, there is a right hemisphere bias for attentional orienting cued by social stimuli, but not for attentional orienting cued by nonsocial stimuli. This supports a theory of a separate neural system for socially cued orienting of attention, as well as a theory of separate parallel and simultaneous neural systems for attention in the two cerebral hemispheres.     

The parietal cortex and attentional modulations of activities of the visual cortex

We recorded high density event-related brain potentials (ERPs) from a patient with focal left parietal damage in a covert visual orienting task requiring detection of targets in the attended or unattended hemifield. A positivity peaking at 120 ms (P1) to the left visual field stimuli was enlarged when attended than unattended and was localized to the right extrastirate cortex. However, spatial attention did not influence the ERPs to the right visual field stimuli. The leftward cue elicited an enlarged P1 relative to the rightward cue. The results suggest that human parietal cortex is critical for the attentional modulation of the neural activities in the extrastriate cortex associated with stimuli in the contralateral hemifield.     

Glutamate receptor binding in the frontal cortex and dorsal striatum of aged rats with impaired attentional set-shifting

Aged Long-Evans rats exhibit deficits in attentional set shifting, an aspect of executive function, relative to adult rats. Impairments in set shifting and spatial learning are uncorrelated in aged rats, indicating a possible dissociation of the effects of ageing in prefrontal versus hippocampal systems. Ionotropic glutamate receptor binding was assessed using an in vitro autoradiography method in young and aged rats. The rats had been tested on a set-shifting task that measured attentional set shifts and reversal learning, as well as in a spatial learning task in the Morris water maze. [3H]Kainate, [3H]AMPA and NMDA-displaceable [3H]glutamate receptor binding were quantified in orbital cortex, cingulate cortex, medial frontal cortex, dorsolateral and dorsomedial striatum. Age-related decreases in [3H]kainate binding were apparent in all regions measured. Similarly, NMDA-displaceable [3H]glutamate binding was decreased in the aged rats in all the regions measured except for the medial frontal area where no age effects were observed. [3H]AMPA receptor binding was preserved with age in all the regions measured. Lower levels of [3H]kainate binding in the cingulate cortex were significantly correlated with poorer set-shifting performance, whereas higher levels of NMDA binding in the dorsomedial striatum were correlated with poorer set-shifting performance. There were no significant correlations between the levels of ionotropic glutamate receptors and performance in the reversal task or spatial learning in the Morris water maze. These results indicate that age-related behavioural deficits in attentional set shifting are selectively associated with neurobiological alterations in the cingulate cortex and dorsomedial striatum.     

The frontal cortex and memory for temporal order

Patients with unilateral frontal- or temporal-lobe excisions and normal control subjects made relative-recency decisions about objects presented sequentially. Several objects within each series were presented in the context of actions to be performed using them, such as "squeeze the sponge", whereas others had only to be named. Both left and right frontal-lobe groups were impaired on order judgements for named items, but their performance was normal for action items. The results suggest that providing salient and distinctive items, involving meaningful actions and multimodal cues, helps compensate for deficits in memory for temporal information associated with frontal-lobe damage.     

Spatiotemporal overlap between brain activation related to saccade preparation and attentional orienting

Recent brain imaging studies provided evidence that the brain areas involved with attentional orienting and the preparation of saccades largely overlap, which may indicate that focusing attention at a specific location can be considered as an unexecuted saccade towards that location (i.e. the premotor theory of attention). Alternatively, it may be proposed that attentional orienting is simply relevant for preparing saccades, but the two processes may also be completely unrelated. In two experiments, we examined temporal activation of brain areas by measuring the electroencephalogram. Central cues indicated the likely side (left or right) at which a to-be-attended target would occur, or to which a saccade had to be prepared. Cue direction-related activity was determined, time-locked to cue onset. In addition, in our second experiment, delayed saccades had to be carried out, which allows to focus on processes strongly related to saccade execution. In nearly all tasks, an early directing attention negativity (EDAN), an anterior directing attention negativity (ADAN), and a late directing attention positivity (LDAP) were observed, time-locked to cue onset. Source analyses supported the view that this activity probably originates from areas within the ventral intraparietal sulcus (vIPS) and the frontal eye fields (FEF). The saccade-locked analysis also indicated that the FEF plays an important role in triggering saccades, but the role of vIPS appears to be minimal. The latter finding disfavors the premotor theory of attention, as it suggests that the relation between attention and action is less direct.     

Electrophysiological evidence for changes in attentional orienting and selection in functional somatic symptoms

ObjectiveWe investigated changes in attention mechanisms in people who report a high number of somatic symptoms which cannot be associated with a physical cause.MethodBased on scores on the Somatoform Disorder Questionnaire (SDQ-20; Nijenhuis et al., 1996) we compared two non-clinical groups, one with high symptoms on the SDQ-20 and a control group with low or no symptoms. We recorded EEG whilst participants performed an exogenous tactile attention task where they had to discriminate between tactile targets following a tactile cue to the same or opposite hand.ResultsThe neural marker of attentional orienting to the body, the Late Somatosensory Negativity (LSN), was diminished in the high symptoms group and attentional modulation of touch processing was prolonged at mid and enhanced at later latency stages in this group.ConclusionThese results confirm that attentional processes are altered in people with somatic symptoms, even in a non-clinical group. Furthermore, the observed pattern fits explanations of changes in prior beliefs or expectations leading to diminished amplitudes of the marker of attentional orienting to the body (i.e. the LSN) and enhanced attentional gain of touch processing.SignificanceThis study shows that high somatic symptoms are associated with neurocognitive attention changes.     

The attentional 'spotlight's' penumbra: center-surround modulation in striate cortex

By enhancing neural activity in respective retinotopic cortical representations attention increases the efficiency with which visual information at a selected location is processed. Behavioral data also suggest that information from the vicinity of the attended region is actively suppressed. In search for a physiological correlate of this 'spotlight's penumbra' we assessed neural responses in retinotopic representations of an attended location and of locations at different distances to it. Relative to passive viewing we found suppressed striate activity for the nearby but not for the far locations. This attention-driven center-surround distribution of neural activity may enhance the contrast between attended and non-attended objects. We relate the different behavior of extrastriate areas to their lower spatial resolution, i.e. larger receptive fields.     

The attentional blink modulates activity in the early visual cortex

The attentional blink (AB) documents a particularly strong case of visual attentional competition, in which subjects' ability to identify a second target (T2) is significantly impaired when it is presented with a short SOA after a first target (T1). We used functional magnetic resonance imaging to investigate the impact of the AB on visual activity in individually defined retinotopic representations of the target stimuli. Our results show reduction of neural response in V3 and marginally in V2 and V1, paralleling the behavioral AB effect. Reduction of visual activity was accompanied by reduced neural response in the inferior parietal cortex. This indicates that attentional competition modulates activity in higher-order parietal regions and the early visual cortex, providing a plausible neural basis of the behavioral AB effect.     

Effects of vestibular rotatory accelerations on covert attentional orienting in vision and touch

Peripheral vestibular organs feed the central nervous system with inputs favoring the correct perception of space during head and body motion. Applying temporal order judgments (TOJs) to pairs of simultaneous or asynchronous stimuli presented in the left and right egocentric space, we evaluated the influence of leftward and rightward vestibular rotatory accelerations given around the vertical head-body axis on covert attentional orienting. In a first experiment, we presented visual stimuli in the left and right hemifield. In a second experiment, tactile stimuli were presented to hands lying on their anatomical side or in a crossed position across the sagittal body midline. In both experiments, stimuli were presented while normal subjects suppressed or did not suppress the vestibulo-ocular response (VOR) evoked by head-body rotation. Independently of VOR suppression, visual and tactile stimuli presented on the side of rotation were judged to precede simultaneous stimuli presented on the side opposite the rotation. When limbs were crossed, attentional facilitatory effects were only observed for stimuli presented to the right hand lying in the left hemispace during leftward rotatory trials with VOR suppression. This result points to spatiotopic rather than somatotopic influences of vestibular inputs, suggesting that cross-modal effects of these inputs on tactile ones operate on a representation of space that is updated following arm crossing. In a third control experiment, we demonstrated that temporal prioritization of stimuli presented on the side of rotation was not determined by response bias linked to spatial compatibility between the directions of rotation and the directional labels used in TOJs (i.e., "left" or "right" first). These findings suggest that during passive rotatory head-body accelerations, covert attention is shifted toward the direction of rotation and the direction of the fast phases of the VOR.     

Rhythms can overcome temporal orienting deficit after right frontal damage

The main aim of this study was to test whether the use of rhythmic information to induce temporal expectations can overcome the deficit in controlled temporal preparation shown by patients with frontal damage (i.e. temporal orienting and foreperiod effects). Two tasks were administered to a group of 15 patients with a frontal brain lesion and a group of 15 matched control subjects: a Symbolic Cued Task where the predictive information regarding the time of target appearance was provided by a symbolic cue (short line-early vs. long line-late interval) and a Rhythm Cued Task where the predictive temporal information was provided by a rhythm (fast rhythm-early vs. slow rhythm-late interval). The results of the Symbolic Cued Task replicated both the temporal orienting deficit in right frontal patients and the absence of foreperiod effects in both right and left frontal patients, reported in our previous study (Triviño, Correa, Arnedo, &; Lupiañez, 2010). However, in the Rhythm Cued Task, the right frontal group showed normal temporal orienting and foreperiod effects, while the left frontal group showed a significant deficit of both effects. These findings show that automatic temporal preparation, as induced by a rhythm, can help frontal patients to make effective use of implicit temporal information to respond at the optimum time. Our neuropsychological findings also provide a novel suggestion for a neural model, in which automatic temporal preparation is left-lateralized and controlled temporal preparation is right-lateralized in the frontal lobes.     

Scopolamine reduces frontal cortex perfusion

While the cognitive deficits of Alzheimer's disease are considered related to a cholinergic deficit, no attempt has yet been made to test the hypothesis that the characteristic regional cerebral blood flow (rCBF) pattern of Alzheimer's disease may also relate to such a deficit. We therefore measured rCBF using the [133Xe] inhalation technique in 15 young normal subjects before and after induction of reversible cholinergic blockade with scopolamine at doses of 6.1 and 7.3 micrograms/kg i.v. Significant cognitive impairment was observed at both doses, while rCBF changes occurred only at the higher dose. Global CBF was significantly reduced 25 min after scopolamine. The pattern of regional change in CBF was not similar to Alzheimer's disease. Rather than a focal parietotemporal deficit as seen in Alzheimer's disease, we observed a predominantly frontal reduction in flow of about 20%. These results suggest that the frontal but not the parietotemporal deficits seen in several dementing conditions may be related to cholinergic dysfunction.     

Supervisory attentional system in patients with focal frontal lesions

The aim of this study was to re-examine the hypothesis of a link between frontal cortex and the Supervisory Attentional System (SAS; Shallice, 1988). Contrary to previous studies that examined patients with lesions extending beyond the frontal lobes (Shallice, 1982; Burgess & Shallice, 1996a, 1996b), SAS or executive functions were evaluated in a group of patients with strict frontal lesions. Three tasks (Tower of London -TOL-, Hayling and Brixton tests) designed to assess specific SAS processes (planning, inhibition and abstraction of logical rules respectively) were administered. In the TOL test, although frontal patients were slower than control participants, the two groups did not differ in their ability to solve problems. Furthermore, the two groups did not differ in terms of performance in the Hayling and Brixton tests either. These results are discussed in terms of the SAS model and are compared to those observed by Shallice (1982) and Burgess & Shallice (1996a, 1996b). Additionally, the issue of the neural subtract of executive functions is addressed.     

Adult and embryonic frontal cortex transplants after frontal cortex ablation enhance recovery on a reinforced alternation task

Damage to the medial frontal cortex in rats results in a learning deficit on a reinforced alternation task. The rate of recovery from this deficit was accelerated by transplantation of either adult or embryonic frontal cortex, provided that a delay was introduced between injury and transplantation. The rates of recovery for both delayed embryonic and adult transplants did not differ from the undamaged group. In contrast, transplants of embryonic frontal cortex immediately after ablation did not accelerate the rate of recovery. The accelerated rate of behavioral recovery on the reinforced alternation task appeared to correlate with transplant survival.     

Covert orienting to exogenous and endogenous cues in children with spina bifida

Children with spina bifida meningomyelocele and hydrocephalus (SBM) have congenital dysmorphology of the midbrain and thinning of the posterior cortex, brain regions associated with the control of covert orienting. We studied cued covert orienting in 92 children with SBM, and 40 age-matched typically developing controls. Cues were of three types: exogenous (luminance change in a peripheral box either valid or invalid for upcoming target location), endogenous arrow (a central arrow either valid or invalid for upcoming target location), or endogenous word (a central word either valid or invalid for upcoming target location). Compared to controls, children with SBM showed slowed covert orienting to both exogenous and endogenous cues and a higher cost of attentional disengagement (e.g., a greater cue-validity effect) for exogenous although not for endogenous cues. Covert orienting deficits were associated with midbrain dysmorphology in the form of beaking of the tectum, and with right posterior brain volume loss.     

The squirrel monkey entorhinal cortex: Architecture and medial frontal afferents

The cytoarchitecture of the periallocortex was studied in cresyl-violet-stained frontal and sagittal sections in six adult squirrel monkeys (Saimiri sciureus). The entorhinal area, located between the sulcus semiannularis and sulcus rhinalis in the rostral parahippocampal gyrus, has been divided into a caudal-medial Area 28a and rostral-lateral Area 28b. Of the six paleocortical laminae, Layer II is the most distinctive, for in 28a it consists of a deeply-stained, dense, continuous lamina and in 28b is interrupted into cell islands. Layer IV, lamina dissecans, is thick and irregular in 28b, thin and of uniform thickness in rostral 28a, and disappears in caudal 28a in transition to the isocortex of the more caudal parahippocampal gyrus. Further observations in Fink-Heimer silver material of fiber degeneration resulting from medial prefrontal ablations in these monkeys suggest that Areas 9 and 10 project to superficial layers (Layer II) of 28a whereas the orbital probably projects to the deeper layers (Layer V) of 28b. The topography and laminar specificity of prefrontal-entorhinal connections may have important functional consequences in terms of hippocampal input.