We review evidence for partially segregated networks of brain areas that carry out different attentional functions. One system, which includes parts of the intraparietal cortex and superior frontal cortex, is involved in preparing and applying goal-directed (top-down) selection for stimuli and responses. This system is also modulated by the detection of stimuli. The other system, which includes the temporoparietal cortex and inferior frontal cortex, and is largely lateralized to the right hemisphere, is not involved in top-down selection. Instead, this system is specialized for the detection of behaviourally relevant stimuli, particularly when they are salient or unexpected. This ventral frontoparietal network works as a 'circuit breaker' for the dorsal system, directing attention to salient events. Both attentional systems interact during normal vision, and both are disrupted in unilateral spatial neglect.

Control of goal-directed and stimulus-driven attention in the brain

Recent developments in the quantitative analysis of complex networks, based largely on graph theory, have been rapidly translated to studies of brain network organization. The brain's structural and functional systems have features of complex networks--such as small-world topology, highly connected hubs and modularity--both at the whole-brain scale of human neuroimaging and at a cellular scale in non-human animals. In this article, we review studies investigating complex brain networks in diverse experimental modalities (including structural and functional MRI, diffusion tensor imaging, magnetoencephalography and electroencephalography in humans) and provide an accessible introduction to the basic principles of graph theory. We also highlight some of the technical challenges and key questions to be addressed by future developments in this rapidly moving field.

Complex brain networks: graph theoretical analysis of structural and functional systems

Co-Planar Stereotaxic Atlas of the Human Brain—3-Dimensional Proportional System: An Approach to Cerebral Imaging, J. Talairach, P. Tournoux. Georg Thieme Verlag, New York (1988), 122 pp., 130 figs. DM 268

Functional neuroimaging studies have started unravelling unexpected functional attributes for the posteromedial portion of the parietal lobe, the precuneus. This cortical area has traditionally received little attention, mainly because of its hidden location and the virtual absence of focal lesion studies. However, recent functional imaging findings in healthy subjects suggest a central role for the precuneus in a wide spectrum of highly integrated tasks, including visuo-spatial imagery, episodic memory retrieval and self-processing operations, namely first-person perspective taking and an experience of agency. Furthermore, precuneus and surrounding posteromedial areas are amongst the brain structures displaying the highest resting metabolic rates (hot spots) and are characterized by transient decreases in the tonic activity during engagement in non-self-referential goal-directed actions (default mode of brain function). Therefore, it has recently been proposed that precuneus is involved in the interwoven network of the neural correlates of self-consciousness, engaged in self-related mental representations during rest. This hypothesis is consistent with the selective hypometabolism in the posteromedial cortex reported in a wide range of altered conscious states, such as sleep, drug-induced anaesthesia and vegetative states. This review summarizes the current knowledge about the macroscopic and microscopic anatomy of precuneus, together with its wide-spread connectivity with both cortical and subcortical structures, as shown by connectional and neurophysiological findings in non-human primates, and links these notions with the multifaceted spectrum of its behavioural correlates. By means of a critical analysis of precuneus activation patterns in response to different mental tasks, this paper provides a useful conceptual framework for matching the functional imaging findings with the specific role(s) played by this structure in the higher-order cognitive functions in which it has been implicated. Specifically, activation patterns appear to converge with anatomical and connectivity data in providing preliminary evidence for a functional subdivision within the precuneus into an anterior region, involved in self-centred mental imagery strategies, and a posterior region, subserving successful episodic memory retrieval.

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The precuneus: a review of its functional anatomy and behavioural correlates.

Background and Objectives: There is a substantial body of evidence assessing the effects of equine-assisted therapy on physiological and psychological aspects of individuals with disabilities. This study aimed to evaluate the physiological benefits of this alternative therapy for children with cerebral palsy (CP) by means of a systematic review and meta-analysis. Methods: This systematic review included all randomized and nonrandomized clinical trials of hippotherapy (HT), therapeutic horse riding (THR), and artificial saddle (AS) for the treatment of children with CP by a systematic search in Medline, Embase, Cochrane Library, and other databases up to November 2012. Articles were assessed for inclusion eligibility and quality by two independent reviewers. Any discordant case was re-reviewed and consensus was obtained after sufficient discussion. A random effects model of meta-analysis was applied to provide summary statistics for each outcome. Results: Seven randomized controlled trials (RCTs), 4 non-RCTs, and 7 self-controlled studies were included for quality assessment. Ten studies assessed the effect of HT, 5 evaluated THR, and 3 evaluated AS. The sample size differed from 3 to 72, and the quality ranged from low to moderate. Six studies were included in the meta-analysis, and there was a significant improvement in the 66-item Gross Motor Function Measure (GMFM-66), the GMFM-66/88 total score, and the dimension E of the GMFM. Although the asymmetry score tended to be reduced, it failed to reach statistical significance. Conclusions: HT, THR, and AS seem to improve the total score of the gross motor function via improvement of the walking, running, and jumping dimension. However, they are not likely to be of benefit to the symmetry of postural muscle activity. Studies included in this review lack high-quality RCTs with a sufficient number of subjects, which thus warrants further evaluations of these modalities using large-scale well-designed RCTs.

/pdf/the-effect-of-riding-as-an-alternative-treatment-for-5amnj0qp1l.pdf

The Effect of Riding as an Alternative Treatment for Children with Cerebral Palsy: A Systematic Review and Meta-Analysis

Functional MRI was used to examine cerebral activations in 12 subjects while they performed a spatial attention task. This study applied more stringent behavioural and cognitive controls than previously used for similar experiments: (i) subjects were included only if they showed evidence of attentional shifts while performing the task in the magnet; (ii) the experimental task and baseline condition were designed to eliminate the contributions of motor output, visual fixation, inhibition of eye movements, working memory and the conditional (no-go) component of responding. Activations were seen in all three hypothesized cortical epicentres forming a network for spatial attention: the lateral premotor cortex (frontal eye fields), the posterior parietal cortex and the cingulate cortex. Subcortical activations were seen in the basal ganglia and the thalamus. Although the task required attention to be equally shifted to the left and to the right, eight of 10 subjects showed a greater area of activation in the right parietal cortex, consistent with the specialization of the right hemisphere for spatial attention. Other areas of significant activation included the posterior temporo-occipital cortex and the anterior insula. The temporo-occipital activation was within a region broadly defined as MT+ (where MT is the middle temporal area) which contains the human equivalent of area MT in the macaque monkey. This temporo-occipital area appears to constitute a major component of the functional network activated by this spatial attention task. Its activation may reflect the 'inferred' shift of the attentional focus across the visual scene.

A large-scale distributed network for covert spatial attention: further anatomical delineation based on stringent behavioural and cognitive controls.

Background and Purpose— Although there is some early evidence showing the value of repetitive transcranial magnetic stimulation (rTMS) in stroke rehabilitation, the therapeutic effect of high-frequency rTMS, along with the physiology of rTMS-induced corticomotor excitability supporting motor learning in stroke, has not been established. This study investigated high-frequency rTMS-induced cortical excitability and the associated motor skill acquisition in chronic stroke patients. Methods— Fifteen patients with chronic hemiparetic stroke (13 men; mean age 53.5 years) practiced a complex, sequential finger motor task using their paretic fingers either after 10 Hz or sham rTMS over the contralateral primary motor cortex (M1). Both the changes in the behavior and corticomotor excitability before and after the intervention were examined by measuring the movement accuracy, the movement time, and the motor-evoked potential (MEP) amplitude. A separate repeated-measures ANOVA and correlation statistics were used to determine the main and interaction effects as well as relationship between the changes in the behavioral and corticomotor excitability. Results— High-frequency rTMS resulted in a significantly larger increase in the MEP amplitude than the sham rTMS ( P P Conclusions— High-frequency rTMS of the affected motor cortex can facilitate practice-dependent plasticity and improve the motor learning performance in chronic stroke victims.

http://www.luzimarteixeira.com.br/wp-content/uploads/2010/01/tms-in-chronic-stroke.pdf

Repetitive Transcranial Magnetic Stimulation–Induced Corticomotor Excitability and Associated Motor Skill Acquisition in Chronic Stroke

Functional magnetic resonance imaging (fMRI) was used to determine whether visual responses to food in the human amygdala and related corticolimbic structures would be selectively altered by changes in states of hunger. Participants viewed images of motivationally relevant (food) and motivationally irrelevant (tool) objects while undergoing fMRI in alternately hungry and satiated conditions. Food-related visual stimuli elicited greater responses in the amygdala, parahippocampal gyrus. and anterior fusiform gyrus when participants were in a hungry state relative to a satiated state. The state-dependent activation of these brain structures did not generalize to the motivationally irrelevant objects. These results support the hypothesis that the amygdala and associated inferotemporal regions are involved in the integration of subjective interoceptive states with relevant sensory cues processed along the ventral visual stream.

Hunger selectively modulates corticolimbic activation to food stimuli in humans.

Background and Purpose—Functional MRI (fMRI) studies could provide crucial information on the neural mechanisms of motor recovery in patients with stroke. Resting-state fMRI is applicable to patients with stroke who are not capable of proper performance of the motor task. In this study, we explored neural correlates of motor recovery in patients with stroke by investigating longitudinal changes in resting-state functional connectivity of the ipsilesional primary motor cortex (M1). Methods—A longitudinal observational study using repeated fMRI experiments was conducted in 12 patients with stroke. Resting-state fMRI data were acquired 4 times over a period of 6 months. Patients participated in the first session of fMRI shortly after onset and thereafter in subsequent sessions at 1, 3, and 6 months after onset. Resting-state functional connectivity of the ipsilesional M1 was assessed and compared with that of healthy subjects. Results—Compared with healthy subjects, patients demonstrated higher functional co...

Longitudinal Changes of Resting-State Functional Connectivity During Motor Recovery After Stroke

Functional magnetic resonance imaging (fMRI) was used to determine whether visual responses to food in the human amygdala and related corticolimbic structures would be selectively altered by changes in states of hunger. Participants viewed images of motivationall y relevant (food) and motivationally irrelevant (tool) objects while undergoing fMRI in alternately hungry and satiated conditions. Foodrelated visual stimuli elicited greater responses in the amygdala, parahippocampal gyrus, and anterior fusiform gyrus when participants were in a hungry state relative to a satiated state. The state-dependent activation of these brain structures did not generalize to the motivationally irrelevant objects. These results support the hypothesis that the amygdala and associated inferotemporal regions are involved in the integration of subjective interoceptive states with relevant sensory cues processed along the ventral visual stream. The brain's limited capacity for handling information necessitates the selective allocation of processing resources to stimuli that are relevant to current drives and motivational needs. How the brain assigns salience to environmental cues related to relevant events has yet to be fully understood. The amygdala may play an important role in this process because of its neural connections, which link interoceptive information with information regarding sensory events in the external world (Amaral, Price, Pitkanen, & Carmichael, 1992; Herzog & Van Hoesen, 1976). Although there is support for this function of the amygdala in nonhuman animals, the evidence is more tentative in the human brain. Animal studies have documented that the amygdala and associated limbic forebrain regions play a crucial role in the coordi

Yun-Hee Kim

Papers

A large-scale distributed network for covert spatial attention: further anatomical delineation based on stringent behavioural and cognitive controls.

Repetitive Transcranial Magnetic Stimulation–Induced Corticomotor Excitability and Associated Motor Skill Acquisition in Chronic Stroke

Hunger selectively modulates corticolimbic activation to food stimuli in humans.

Longitudinal Changes of Resting-State Functional Connectivity During Motor Recovery After Stroke

BRIEF COMMUNICATION Hunger Selectively Modulates Corticolimbic Activation to Food Stimuli in Humans