Retrieval from episodic memory: neural mechanisms of interference resolution.

Selectively retrieving a target memory among related memories requires some degree of inhibitory control over interfering and competing memories, a process assumed to be supported by inhibitory mechanisms. Evidence from behavioral studies suggests that such inhibitory control can lead to subsequent forgetting of the interfering information, a finding called retrieval-induced forgetting [Anderson, M. C.

Dissociation of neural correlates of verbal and non-verbal visual working memory with different delays.

Background: Dorsolateral prefrontal cortex (DLPFC), posterior parietal cortex, and regions in the occipital cortex have been identified as neural sites for visual working memory (WM). The exact involvement of the DLPFC in verbal and non-verbal working memory processes, and how these processes depend on the time-span for retention, remains disputed.

Methods: We used functional MRI to explore the neural correlates of the delayed discrimination of Gabor stimuli differing in orientation.

Cortical activation during sequences of memory-guided saccades: a functional MRI study.

Blood oxygenation-level dependent changes in the cerebral cortex were measured using event-related functional magnetic resonance imaging in participants while they performed triple-step memory-guided saccades. To explore the role of dorsolateral prefrontal cortex in the manipulation of the contents of working memory, the sequence of saccade targets in the memory-guided task was either constant or was manipulated using coloured cues. The dorsolateral prefrontal cortex was significantly activated only during the period when participants had to reorder the locations of the saccade targets and not during the maintenance of spatial locations.

Cortical activation during memory-guided saccades.

Using functional magnetic resonance imaging, we compared responses during visually guided saccades with those evoked during memory-guided saccades, in which participants executed saccades to remembered locations. Eye movements were recorded in the magnetic resonance tomograph. Significantly stronger activation during memory-guided saccades was observed in the posterior portion of the right inferior frontal gyrus, in the left inferior frontal eye field, in the posterior parietal cortex, as well as in the right posterior superior temporal gyrus.

Effects of nonspatial selective and divided visual attention on fMRI BOLD responses.

Using an uncertainty paradigm and functional magnetic resonance imaging (fMRI) we studied the effect of nonspatial selective and divided visual attention on the activity of specific areas of human extrastriate visual cortex. The stimuli were single ovals that differed from an implicit standard oval in either colour or width. The subjects' task was to classify the current stimulus as one of two possible alternatives per stimulus dimension.

BOLD response in dorsal areas varies with relative disparity level.

Using fMRI, we explored cortical responses to dichoptically presented random-dot (RD) stimuli which formed a checkerboard by means of horizontal disparity (Julesz). Depth reversals occurred every 800 ms by appropriate horizontal shifting of a subset of the RD pattern. We compared cortical blood oxygen level dependent (BOLD) responses of five subjects under conditions with and without binocular disparity.

Functional magnetic resonance imaging evidence for binocular interactions in human visual cortex.

Using functional magnetic resonance imaging (fMRI), we explored the binocular interactions occurring when subjects viewed dichoptically presented checkerboard stimuli. A flickering radial checkerboard was presented to each eye of the subject, while T2*-weighted images were acquired over the visual cortex with gradient-echo, echoplanar sequences. We compared responses in striate and extrastriate visual cortex under four conditions: both eyes were stimulated at the same time (binocular condition), each eye was stimulated in alternation (monocular condition) or first the one eye then the other eye was stimulated (left eye first - right eye trailing, or vice versa).

Event-related fMRI responses in the human frontal eye fields in a randomized pro- and antisaccade task.

We examined whether the frontal eye fields (FEF) are involved in the suppression of reflexive saccades. Simultaneous recording of horizontal eye movements and functional magnetic resonance imaging enabled us to perform a randomized pro- and antisaccade task and to sort blood oxygenation level dependent (BOLD) time series on the basis of task performance. Saccadic reaction time distributions were comparable across tasks indicating a similar effort in preprocessing of the saccades.