Perirhinal cortex ablation in rats selectively impairs object identification in a simultaneous visual comparison task.

In Experiment 1, rats discriminated among computer-generated visual displays (scenes) comprising 3 different shapes (objects). One constant scene (unrewarded) appeared on every trial together with a trial-unique variable scene (rewarded). Four types of variable scene were intermingled: (a) unfamiliar objects in different positions from the constant; (b) unfamiliar objects in same positions as the constant; (c) same objects as the constant in different positions; (d) same objects and positions, recombined. Aspiration lesions of perirhinal cortex impaired performance with type (b) only. Experiment 2 tested spatial delayed nonmatching-to-sample. The perirhinal group were impaired nonsignificantly, and less than fornix-transected rats in an earlier study. Rats' perirhinal cortex, like monkeys', subserves object identification in the absence of memory requirement but does not contribute substantially to hippocampal system spatial memory function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The offset of childhood amnesia: Memory for events that occurred before age 3.

Adult memory for the events surrounding the birth of a sibling was examined in 69 adults. The authors identified a steep offset for childhood amnesia for this event before the child reaches age 2? years. The authors also examined the accuracy of information recalled. Although the majority of the answers were accurate, false memories were a consistent feature of the data. Alternative explanations of the authors' data were considered by examining the amount of information an additional 57 adults had about a family birth for which they could have no memory. The pattern of results did not support the view that participants might be unable to differentiate between memories and knowledge about the event. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flood Tide: sonification as musical performance—an audience perspective

The number of events and artifacts described as sonification has increased considerably in recent years with some works making a bridge between the representation of data and artistic expression. Flood Tide which sonifies the flow of tidal water is such a work and has achieved a relatively high profile attracting good audiences for its 10 performances to date. It is not entirely obvious however what it is that attracts audiences and whether it is effective at representing the data being sonified. This paper aims to address these issues and is based on a discussion group in which these and other questions are considered.     

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)     

Spatial memory impairment in rats with fornix transection is not accompanied by a simple encoding deficit for directions of objects in visual space.

In Experiment 1, rats learned 6 discriminations among pairs of complex wide-angle visual displays, presented concurrently, using a computer-controlled Y maze. Fornix-transected rats were unimpaired relative to controls regardless of whether the displays comprised a single large "objectlike" figure or "scenelike" arrays of spatially distributed figures. Experiment 2 compared 2 versions of a visual discrimination in which either object identity (independent of location within the visual field) or location within the visual field (independent of object identity) had to be used. The fornix-transected rats performed normally with either cue. In Experiment 3, however, the same group was clearly impaired on a standard spatial memory test, spatial delayed nonmatching to sample. Although the fornix-transected rats were more likely to choose rapidly and inaccurately, their deficit was not a by-product of impulsive responding. The spatial impairment was not merely a difficulty in encoding direction of a single item within visual space, but more complex configural deficits could not be ruled out. (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)     

The recognition memory deficit caused by mediodorsal thalamic lesion in non-human primates: a comparison with rhinal cortex lesion

Two earlier studies found that rhinal cortex ablations in the monkey (Macaca fascicularis) impaired delayed matching-to-sample (DMS) when the stimuli in the experiment came from a large population of possible stimuli, but not when the stimulus population was small, while uncinate fascicle section had no effect on DMS whatever the stimulus population size. The mediodorsal thalamus receives a large projection from the rhinal cortex, and has been implicated in recognition memory performance. We trained monkeys preoperatively in delayed matching-to-sample with large and small stimulus populations, exactly as in the earlier studies, then examined the effect of bilaterally ablating the medial portion of the mediodorsal thalamic nucleus. Mediodorsal lesion impaired postoperative delayed matching-to-sample performance with a large stimulus set, but had no effect on performance of DMS with a small stimulus population. In comparison with the earlier data from rhinal cortex lesions with the same methods, wherever a deficit was seen in the rhinal-lesioned animals the mediodorsal thalamic nucleus-lesioned animals showed a smaller deficit. We conclude that other efferents from the rhinal cortex, possibly those to the adjacent inferior temporal cortex, enable better performance in the mediodorsal thalamic nucleus-lesioned animals than in the animals with rhinal cortex ablation.     

The Role of Perirhinal Cortex in Visual Discrimination Learning for Visual Secondary Reinforcement in Rats.

Perirhinal cortex in monkeys has been thought to be involved in visual associative learning. The authors examined rats' ability to make associations between visual stimuli in a visual secondary reinforcement task. Rats learned 2-choice visual discriminations for secondary visual reinforcement. They showed significant learning of discriminations before any primary reinforcement. Following bilateral perirhinal cortex lesions, rats continued to learn visual discriminations for visual secondary reinforcement at the same rate as before surgery. Thus, this study does not support a critical role of perirhinal cortex in learning for visual secondary reinforcement. Contrasting this result with other positive results, the authors suggest that the role of perirhinal cortex is in "within-object" associations and that it plays a much lesser role in stimulus-stimulus associations between objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)