Development of Attentional and Oculomotor Control.

The present study was conducted to examine the development of attentional and oculomotor control. More specifically, the authors were interested in the development of the ability to inhibit an incorrect but prepotent response to a salient distractor. Participants, who ranged in age from 8 to 25 years, performed 3 different eye movement tasks: a prosaccade, an antisaccade, and an oculomotor capture task. The time required to initiate a saccade decreased with age across all 3 tasks. Consistent with previous reports, accuracy was relatively age invariant in the prosaccade task. Performance improved with age, asymptoting at 16 years in the antisaccade task. It is interesting to note that despite the superficial similarity of the antisaccade and oculomotor capture tasks, performance was relatively age invariant in the latter. These results are discussed in terms of developmental differences in the interaction of goal-directed and stimulus-driven processes in the control of attention and action. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociable Effects of Lesions to the Perirhinal Cortex and the Postrhinal Cortex on Memory for Context and Objects in Rats.

Memory for the context in which an object appeared was investigated with a version of the spontaneous object recognition paradigm. Sham-operated rats explore familiar objects appearing in incongruent but familiar contexts more than those appearing in congruent contexts, revealing memory for the context in which an object previously appeared. At short delays, perirhinal cortex-lesioned rats were unimpaired on memory for object in context, whereas fornix-lesioned rats showed only a mild impairment. In contrast, postrhinal lesions resulted in severe deficits. However, in a comparable noncontextual object task, postrhinal and fornix lesions had no effect, whereas perirhinal-lesioned rats were severely impaired. Comparison of these tasks and other published data may shed light on the nature of the contextual processing involved. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging and the Strategic Control of the Fixation Offset Effect.

A study was conducted to examine potential age-related differences in the strategic control of exogenous and endogenous saccades within the context of the fixation offset effect (FOE; i.e., faster saccades when a fixation point is removed than when it is left on throughout a trial). Subjects were instructed to make rapid saccades either on the basis of a suddenly appearing peripheral visual stimulus (exogenous saccade) or in response to a tone (endogenous saccade). On half of the trials the fixation point was removed simultaneously with the occurrence of the cue stimulus. Subjects' preparatory set was varied by manipulating the proportion of saccades generated to a visual and auditory stimulus within a trial block. Young and old adults both produced FOEs, and the FOEs were strategically modulated by preparatory set. The data are discussed in terms of aging and oculomotor control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential Prefrontal Cortex Activation During Inhibitory Control in Adolescents With and Without Childhood Attention-Deficit/Hyperactivity Disorder.

The authors examined inhibitory control processes in 8 adolescents diagnosed with attention-deficit/ hyperactivity disorder (ADHD) during childhood and in 8 adolescent control participants using functional MRI with the Stimulus and Response Conflict Tasks (K. W. Nassauer & J. M. Halperin, 2003). No group differences in performance were evident on measures of interference control and/or response competition created by location and direction stimuli. However, the ADHD group demonstrated significantly greater activation of the left ventrolateral prefrontal cortex during interference control as well as greater activation of the left anterior cingulate cortex, right ventrolateral prefrontal cortex, and left basal ganglia during the dual task of interference control and response competition. The magnitude of the prefrontal and basal ganglia activation was positively correlated with severity of ADHD. Response competition alone did not yield group differences in activation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Objects and Positions in Visual Scenes: Effects of Perirhinal and Postrhinal Cortex Lesions in the Rat.

The authors assessed rats' encoding of the appearance or egocentric position of objects within visual scenes containing 3 objects (Experiment 1) or 1 object (Experiment 2A). Experiment 2B assessed encoding of the shape and fill pattern of single objects, and encoding of configurations (object + position, shape + fill). All were assessed by testing rats' ability to discriminate changes from familiar scenes (constant-negative paradigm). Perirhinal cortex lesions impaired encoding of objects and their shape; postrhinal cortex lesions impaired encoding of egocentric position, but the effect may have been partly due to entorhinal involvement. Neither lesioned group was impaired in detecting configural change. In Experiment 1, both lesion groups were impaired in detecting small changes in relative position of the 3 objects, suggesting that more sensitive tests might reveal configural encoding deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manipulation of gonadal hormones in neonatal rats alters the morphological response of cortical neurons to brain injury in adulthood.

The authors examined the effects of sex and neonatal hormones on the response of pyramidal cells (Layer III, parietal cortex) to injury of the medial frontal cortex in the adult rat. At birth, males were gonadectomized (GDX) or sham-operated. Females were given testosterone (T) or oil injections. In adulthood, rats that had been left intact at birth were GDX, and they then received bilateral medial frontal cortex lesions or sham surgery. Rats not exposed to T at birth exhibited losses of dendritic arbor (males GDX at birth) or dendritic spine density (oil-treated females). Compensation after cortical injury is dependent on the rat's sex and history of exposure to gonadal steroids. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correlations of Regional Cerebral Metabolism With Memory Performance and Executive Function in Patients With Herpes Encephalitis or Frontal Lobe Lesions.

Cerebral [1?F]fluorodeoxyglucose positron emission tomography (1?FDG-PET) data from patients suffering amnesia following herpes encephalitis (n = 7) or frontal lobe pathology (n = 14) were compared with data from age-matched nonamnesic subjects (n = 10). All subjects received structural MRI, resting 1?FDG-PET scans, and neuropsychological evaluation. PET data were analyzed using complementary statistical parametric mapping and region-of-interest methods. Differential patterns of hypometabolism were found in patients relative to healthy controls. Factor analysis of the neuropsychological data revealed that memory performance was associated with retrosplenial and medial temporal metabolism, and executive function was associated with dorsolateral frontal metabolism. The association between memory performance and retrosplenial metabolism remained statistically significant after accounting for measures of cerebral atrophy using MRI. The significance of the retrosplenium as a major relay station between the thalamus and the medial temporal and frontal lobes--sensitive to changes in either--is discussed in the light of the findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibitory Control in Rats Performing a Stop-Signal Reaction-Time Task: Effects of Lesions of the Medial Striatum and d-Amphetamine.

The stop-signal task measures the ability to inhibit a response that has already been initiated, that is, the ability to stop. Imaging studies have implicated frontostriatal circuitry in the mediation of this form of response control. The authors report inhibition functions of normal rats and those with medial striatal damage performing the stop-signal task. Excitotoxic lesions of the medial striatum produced significant deficits on task performance, including increased omissions on the go task and flattened inhibition function, possibly as a result of increased reaction-time mean and variability. Medial striatal lesions also significantly slowed stop-signal reaction time. Subsequent treatment with d-amphetamine removed (0.3 mg/kg) or exacerbated (1.0 mg/kg) this deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)