Human functional MRI studies frequently reveal the joint activation of parietal and of lateral and mesial frontal areas during various cognitive tasks. To analyze the geometrical organization of those networks, we used an automatized clustering algorithm that parcels out sets of areas based on their similar profile of task-related activations or deactivations. This algorithm allowed us to reana...

Although the parietal lobe is not traditionally thought to support declarative memory, recent event-related fMRI studies of episodic retrieval have consistently revealed a range of memory-related influences on activation in lateral posterior parietal cortex (PPC) and precuneus extending into posterior cingulate and retrosplenial cortex. This article surveys the fMRI literature on PPC activation...

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 foll...

Various models of executive control predict that practice should modulate the recruitment of executive brain mechanisms. To investigate this issue, we asked 15 participants to perform a cued global/local attention task while brain activity was recorded with event-related functional magnetic resonance imaging (fMRI). Practice significantly reduced the recruitment of left inferior parietal region...

The present study evaluated patterns of electrophysiological activity associated with sustained vigilance in healthy adults. Quantitative electroencephalographs (QEEG) were recorded during the performance of a Continuous Performance Test (CPT). Participants were divided into low and high vigilance groups based upon their reaction time changes between the early and late portions of the CPT. Cohe...

Humans and animals use landmarks during wayfinding to determine where they are in the world and to guide their way to their destination. To implement this strategy, known as landmark-based piloting, a navigator must be able to: (i) identify individual landmarks, (ii) use these landmarks to determine their current position and heading, (iii) access long-term knowledge about the spatial relations...

The Clock Drawing Test has been systematically used to assess visuospatial deficits related to the parietal lobes, but we now acknowledge its much more complex relation with other cognitive abilities. Despite its common use in clinical and investigational practices, no study has developed normative data for the Portuguese population. We present the distribution of clock drawing scores using thr...

The functional relevance of brain activity during visuospatial tasks was investigated by combining functional magnetic resonance imaging with unilateral repetitive transcranial magnetic stimulation (rTMS). The cognitive tasks involved visuospatial operations on visually presented and mentally imagined material ("mental clock task"). While visuospatial operations were associated with activation ...

Based on neuroimaging methods, it is a commonly held view that numerical representation in the human parietal lobes is format independent. We used a transcranial magnetic stimulation adaptation paradigm to examine the existence of functionally segregated overlapping populations of neurons for different numerical formats and to reveal how numerical information is encoded and represented. Based o...

Objective To investigate neural correlates associated with recovery of motor function over 6 months in patients with basal ganglia (BG) stroke using acetazolamide (ACZ) stress brain-perfusion single-photon emission computed tomography (SPECT). Methods Medical records of 22 patients presenting first-ever BG stroke were retrospectively reviewed. Regional cerebral blood flow (CBF) and cerebrovas...