EFFECTS OF ASPIRATION VERSUS NEUROTOXIC LESIONS OF THE AMYGDALA ON EMOTIONAL RESPONSES IN MONKEYS

All previous reports describing alterations in emotional reactivity after amygdala damage in monkeys were based on aspiration or radiofrequency lesions which likely disrupted fibers of passage coursing to and from adjacent ventral and medial temporal cortical areas. To determine whether this associated indirect damage was responsible for some or all of the changes described earlier, we compared the changes induced by aspiration of the amygdala to those induced by fiber-sparing neurotoxic lesions. Four different stimuli, two with and two without a social component, were used to evaluate the expression of Defense, Aggression, Submission, and Approach responses. In unoperated controls, Defense and Approach behaviors were elicited by all four stimuli, "social" and inanimate alike, whereas Aggression and Submission responses occurred only in the presence of the two "social" stimuli. Furthermore, all Defense reactions were reduced with an attractive inanimate item, while Freezing was selectively increased with an aversive one. Relative to controls, monkeys with neurotoxic amygdala lesions showed the same array of behavioral changes as those with aspiration lesions, namely reduced fear and aggression, increased submission, and excessive manual and oral exploration. Even partial neurotoxic lesions involving less than two-thirds of the amygdala significantly altered fear and manual exploration. These findings convincingly demonstrate that the amygdala is crucial for the normal regulation of emotions in monkeys. Nevertheless, since some of the symptoms observed after neurotoxic lesions were less marked than those seen after aspiration lesions, the emotional disorders described earlier after amygdalectomy in monkeys were likely exacerbated by the attendant fiber damage

Pulvinar Inactivation Disrupts Selection of Movement Plans

The coordinated movement of the eyes and hands under visual guidance is an essential part of goal-directed behavior. Several cortical areas known to be involved in this process exchange projections with the dorsal aspect of the thalamic pulvinar nucleus, suggesting that this structure may play a central role in visuomotor behavior. Here, we used reversible inactivation to investigate the role of the dorsal pulvinar in the selection and execution of visually guided manual and saccadic eye movements in macaque monkeys. We found that unilateral pulvinar inactivation resulted in a spatial neglect syndrome accompanied by visuomotor deficits including optic ataxia during visually guided limb movements. Monkeys were severely disrupted in their visually guided behavior regarding space contralateral to the side of the injection in several domains, including the following: (1) target selection in both manual and oculomotor tasks, (2) limb usage in a manual retrieval task, and (3) spontaneous visual exploration. In addition, saccades into the ipsilesional field had abnormally short latencies and tended to overshoot their mark. None of the deficits could be explained by a visual field defect or primary motor deficit. These findings highlight the importance of the dorsal aspect of the pulvinar nucleus as a critical hub for spatial attention and selection of visually guided actions

Neocerebellar Crus I Abnormalities Associated with a Speech and Language Disorder Due to a Mutation in FOXP2

Bilateral volume reduction in the caudate nucleus has been established as a prominent brain abnormality associated with a FOXP2 mutation in affected members of the ‘KE family’, who present with developmental orofacial and verbal dyspraxia in conjunction with pervasive language deficits. Despite the gene’s early and prominent expression in the cerebellum and the evidence for reciprocal cerebellum-basal ganglia connectivity, very little is known about cerebellar abnormalities in affected KE members. Using cerebellum-specific voxel-based morphometry (VBM) and volumetry, we provide converging evidence from subsets of affected KE members scanned at three time points for grey matter (GM) volume reduction bilaterally in neocerebellar lobule VIIa Crus I compared with unaffected members and unrelated controls. We also show that right Crus I volume correlates with left and total caudate nucleus volumes in affected KE members, and that right and total Crus I volumes predict the performance of affected members in non-word repetition and non-verbal orofacial praxis. Crus I also shows bilateral hypo-activation in functional MRI in the affected KE members relative to controls during non-word repetition. The association of Crus I with key aspects of the behavioural phenotype of this FOXP2 point mutation is consistent with recent evidence of cerebellar involvement in complex motor sequencing. For the first time, specific cerebello-basal ganglia loops are implicated in the execution of complex oromotor sequences needed for human speech

Frontal and insular input to the dorsolateral temporal pole in primates: Implications for auditory memory

The temporal pole (TP) has been involved in multiple functions from emotional and social behavior, semantic processing,memory, language in humans and epilepsy surgery, to the fronto-temporal neurodegenerative disorder (semantic) dementia. However, the role of the TP subdivisions is still unclear, in part due to the lack of quantitative data about TP connectivity. This study focuses in the dorsolateral subdivision of the TP: area 38DL. Area 38DL main input originates in the auditory processing areas of the rostral superior temporal gyrus. Among other connections, area 38DL conveys this auditory highly processed information to the entorhinal, rostral perirhinal, and posterior parahippocampal cortices, presumably for storage in long-term memory (Muñoz-López et al., 2015). However, the connections of the TP with cortical areas beyond the temporal cortex suggest that this area is part of a wider network. With the aim to quantitatively determine the topographical, laminar pattern and weighting of the lateral TP afferents from the frontal and insular cortices, we placed a total of 11 tracer injections of the fluorescent retrograde neuronal tracers Fast Blue and Diamidino Yellow at different levels of the lateral TP in rhesus monkeys. The results showed that circa 50% of the total cortical input to area 38DL originates in medial frontal areas 14, 25, 32, and 24 (25%); orbitofrontal areas Pro and PAll (15%); and the agranular, parainsular and disgranular insula (10%). This study sets the anatomical bases to better understand the function of the dorsolateral division of the TP. More specifically, these results suggest that area 38DL forms part of the wider limbic circuit that might contribute, among other functions, with an auditory component to multimodal memory processing

Cerebral Memory Circuits

This chapter focuses on how the primate forebrain might be organized at the systems level to yield both stimulus memmy (i.e., recognition and recall) and habit formation (i.e., stimulus-response [S-R] learning). Derived mainly from studies in monkeys, the following hypotheses are proposed: (a) stimulus recognition depends on the fonnation of a Hebbian "cell assembly" in a c:ortical sensory processing pathway; the cells are "assembled" by action of a feedback circuit running from the sensmy pathway, through limbic structures, to chemical neuromodulatory systems (e.g., cholinergic, noradrenergic, serotonergic), and then back to the limbic structures and the sensory pathway; (b) stimulus recall depends on the formation of a Hebbian "phase sequence," consisting of one cell assembly linked to another via limbic structures, by action of the same feedback circuit as outlined above; (c) S-R learning depends on linking a c:ortically processed sensory input to an extrapyramidally generated motor output through the fee pack action of chemical neuromodulatory (e.g., dopaminergic) systems on sensory-neostriata( connections. Each of these hypotheses is elaborated and its psychological implications discussed

Effects of selective ablations of the temporal lobes on the visually guided behavior of monkeys and baboons.

Different models of cerebral organization in vision bave been proposed by Lashley (24), Kohler and Wallach (18), and Hebb (ll). Proper evaluation of these theories is hindered by inadequate or inconsistent data pertaining to the locus and extent of the cerebral areas necesaary for normal visual functions, the degree of specialization within these regions, and the types of disturbance produced by their removal. [...

Word recognition as a function of retinal locus.

No contemporary psychologist would deny that the problems of learning and perception are intimately related. But how they are related and the degree to which they are interdependent has never been considered systematically. Hilgard (6, p. 181) has pointed to what is in all probability the major stumbling block. Leading theorists have been too long preoccupied with either one or the other of the two fields of investigation, and it can be fairly said that they have neglected the relationship between them. Kohler (9, p. 192), for example, would have us believe that if past experience does exert an influence upon perceptual organization, “it must be restricted to particular situations”. Furthermore, those who believe otherwise “will have to support their theory by experiments of their own”. Certainly the evidence gathered in support of the Gestalt view (8), (10), (18) is voluminous and persuasive.[...