Danuta M. Kowalska

The role of the inferior prefrontal convexity in performance of delayed nonmatching-to-sample ☆

Findings in an earlier study (Bachevalier, J. and Mishkin, M. Behav. Brain Res. 20, 249-261, 1986) indicated that ventromedial prefrontal cortex, which receives thalamic projections from the limbo-diencephalic system, is critical for visual recognition; whereas the dorsolateral prefrontal cortex, which receives no such thalamic projections, makes little or no contribution to this type of memory. In the present study, we examined the role in recognition of another prefrontal area outside the thalamic projection zone of the limbo-diencephalic system, namely, the inferior prefrontal convexity. In the first experiment, monkeys with lesions of this cortex (Group IC) were found to be impaired in relearning delayed nonmatching-to-sample (DNMS), but not on the subsequent DNMS performance test in which memory demands were greatly increased. In a second experiment, monkeys with combined lesions of the inferior and dorsolateral prefrontal cortex (Group LAT) were also found to be impaired in relearning DNMS, but in this case they were impaired, in addition, on the subsequent performance test. Neither group (IC or LAT) showed retardation in acquiring visual discrimination habits. Analysis of the DNMS behavior of both groups suggested that their deficits on this task were due not to a loss in recognition memory, but to various forms of perseverative interference. The results support the view that the inferior prefrontal convexity, like the dorsolateral prefrontal cortex, lies outside the limbo-diencephalic memory system not only anatomically but also functionally.

Fos imaging reveals differential neuronal activation of areas of rat temporal cortex by novel and familiar sounds

To provide information about the possible regions involved in auditory recognition memory, this study employed an imaging technique that has proved valuable in the study of visual recognition memory. The technique was used to image populations of neurons that are differentially activated by novel and familiar auditory stimuli, thereby paralleling previous studies of visual familiarity discrimination. Differences evoked by novel and familiar sounds in the activation of neurons were measured in different parts of the rat auditory pathway by immunohistochemistry for the protein product (Fos) of the immediate early gene c‐fos. Significantly higher counts of stained neuronal nuclei (266 ± 21/mm2) were evoked by novel than by familiar sounds (192 ± 17/mm2) in the auditory association cortex (area Te3; AudA). No such significant differences were found for the inferior colliculus, primary auditory cortex, postrhinal cortex, perirhinal cortex (PRH), entorhinal cortex, amygdala or hippocampus. These findings are discussed in relation to the results of lesion studies and what is known of areas involved in familiarity discrimination for visual stimuli. Differential activation is produced by novel and familiar individual stimuli in sensory association cortex for both auditory and visual stimuli, whereas the PRH is differentially activated by visual but not auditory stimuli. It is suggested that this latter difference is related to the nature of the particular auditory and visual stimuli used.

Neither perirhinal/entorhinal nor hippocampal lesions impair short-term auditory recognition memory in dogs.

Visual, tactile, and olfactory recognition memory in animals is mediated in part by the perirhinal/entorhinal (or rhinal) cortices and, possibly, the hippocampus. To examine the role of these structures in auditory memory, we performed rhinal, hippocampal, and combined lesions in groups of dogs trained in auditory delayed matching-to-sample with trial-unique sounds. The sample sound was presented through a central speaker and, after a delay, the sample sound and a different sound were played alternately through speakers placed on either side of the animal; the animal was rewarded for responding to the side emitting the sample sound. None of the lesion groups showed significant impairment in comparison either to their own preoperative performance or to the performance of intact control dogs. This was the case both for relearning the delayed matching rule at a delay of 1.5 s and for task performance at variable delays ranging from 10 to 90 s. From these findings we suggest that the tissue critical for auditory recognition memory is located outside both the perirhinal/entorhinal cortices and the hippocampus.

Cognitive functions of the temporal lobe in the dog: a review.

1 The current paper reviews the role of temporal lobe structures in learning and different kinds of memory, with an emphasis on behavioral tasks that re auditory stimuli. 2 The effects of lesions to structures in the temporal lobe were examined in separate groups of dogs, which were trained on an auditory spatial delayed response, or in a trial-unique auditory delayed match to sample recognition task. 3 Spatial memory was impaired after bilateral hippocampal lesions. On the other hand, neither an anterior temporal lesion or rhinal cortical injury nor combined lesion to the hippocampus and the anterior temporal lobe, affected postoperative retraining and performance of the spatial task. 4 Auditory recognition memory task was not impaired after a hippocampal and/or rhinal cortex lesion. However, postoperative retraining of the task was impaired after a lesion to auditory association areas. 5 These results confirm the role of the hippocampus in spatial memory in the dog. On the other hand, the organization of auditory recognition functions within the temporal lobe appears to be different from those described for visual recognition functions.

Different effects of lesions to auditory core and belt cortex on auditory recognition in dogs.

Auditory recognition memory, in contrast to memory in other modalities, is not affected by damage to the perihinal cortex, and its neural basis remains unknown. In an attempt to elucidate this problem, we investigated the role of canine auditory core and belt areas in auditory recognition. Either core or posterior belt areas were surgically removed. The core and belt regions were defined on the basis of response properties and thalamocortical connectivity established in previous studies. The animals were tested on auditory delayed matching to sample (DMS, a recognition memory task) using complex, trial-unique auditory stimuli. Both core and belt lesions impaired auditory recognition, however, the underlying deficit was different. Lesions to the core areas impaired auditory localization abilities. Lesions to the posterior belt areas did not affect this component of the recognition task, but affected auditory quality discrimination and/or recognition. The deficit following the posterior belt lesion did not increase with retention delay, suggesting that auditory belt areas do not constitute a substrate for auditory recognition memory. Their main function appears to be processing of complex sound patterns, including immediate recognition.

Rhinal and dorsolateral prefrontal cortex lesions produce selective impairments in object and spatial learning and memory in canines.

To examine the effects of rhinal and dorsolateral prefrontal cortex lesions on object and spatial recognition memory in canines, we used a protocol in which both an object (delayed nonmatching to sample, or DNMS) and a spatial (delayed nonmatching to position or DNMP) recognition task were administered daily. The tasks used similar procedures such that only the type of stimulus information to be remembered differed. Rhinal cortex (RC) lesions produced a selective deficit on the DNMS task, both in retention of the task rules at short delays and in object recognition memory. By contrast, performance on the DNMP task remained intact at both short and long delay intervals in RC animals. Subjects who received dorsolateral prefrontal cortex (dlPFC) lesions were impaired on a spatial task at a short, 5‐second delay, suggesting disrupted retention of the general task rules; however, this impairment was transient, and long‐term spatial memory performance was unaffected in dlPFC subjects. The present results provide support for the involvement of the RC in object, but not visuospatial, processing and recognition memory, whereas the dlPFC appears to mediate retention of a nonmatching rule. These findings support theories of functional specialization within the medial temporal lobe and frontal cortex and suggest that rhinal and dorsolateral prefrontal cortices in canines are functionally similar to analogous regions in other mammals. J. Comp. Neurol. 511:257–270, 2008.