Contrasting hippocampal and perirhinal cortex function using immediate early gene imaging.

The perirhinal cortex and hippocampus have close anatomical links, and it might, therefore, be predicted that they have close, interlinked roles in memory. Lesion studies have, however, often failed to support this prediction, providing dissociations and double dissociations between the two regions on tests of object recognition and spatial memory. In a series of rat studies we have compared these two regions using the expression of the immediate early gene c-fos as a marker of neuronal activity. This gene imaging approach makes it possible to assess the relative involvement of different brain regions and avoids many of the limitations of the lesion approach. A very consistent pattern of results was found as the various hippocampal subfields but not the perirhinal cortex show increased c-fos activity following tests of spatial learning. In contrast, the perirhinal cortex but none of the hippocampal subfields show increased c-fos activity when presented with novel rather than familiar visual objects. When novel scenes are created by the spatial rearrangement of familiar objects it is the hippocampus and not the perirhinal cortex that shows c-fos changes. This double dissociation for gene expression accords with that found from lesion studies and highlights the different contributions of the perirhinal cortex and hippocampus to memory.     

On immediate function

Behavior is a property of living organisms, not of inanimate matter. The problems of physical science are to understand how a phenomenon works; biological science adds the questions of what a phenomenon does and how something that does such things came to be. Exclusive dedication to cause–effect explanations ignores how behavior helps creatures cope with their internal and external environments. Laws of causation describe the precursors to behavior; laws of function describe the effects of behavior. The numerous instances of learning reflect the many ways that selective pressure for altering behavior on the basis of experience has been manifested. Little basis exists for assuming that the various forms of learning reflect either common functions or common processes. Instead, it seems that evolutionary processes have resulted in domain-specific learning. The rules of learning must be understood in terms of the function that the particular manifestation of learning serves for the organism. Evolutionary theory provides the framework for understanding function as well as relations between function and causal mechanisms.     

Brain MR kurtosis imaging study: Contrasting gray and white matter

This paper mainly focuses on characterization of different brain tissues such as White and Gray matter (WM and GM) using the relation between Diffusion Tensor Imaging and Diffusion Kurtosis Imaging parameters. Both Diffusion Tensor Imaging and Diffusion Kurtosis Imaging are the extension of Diffusion Weighted Imaging, which are widely applied for analysing micro fibre structure of human organs non-invasively. Diffusion Tensor Imaging assumes that the water diffusion is in Gaussian nature and Diffusion Kurtosis Imaging accounts the deviation of the Gaussian nature. This study, conducted a correlation and regression analysis between different parametric maps generated from Diffusion Kurtosis Images. For this we have chosen 200 regions of interest pixels drawn from brain MRIs. From the results, it is observed that there is a significant variation in the correlation results between Axial Diffusion and Kurtosis Fractional Anisotropy maps of Gray matter and White matter tissues. This can be employed for enhancing accuracy in MRI segmentation techniques and also as a potential tool for Neuro degenerative disease detection.     

The immediate and sustained effects of acute exercise on planning aspect of executive function

ObjectiveThe purpose of this study was to clarify the immediate and sustained effects of an acute bout of exercise on the planning aspects of executive function.DesignThis study used a 2 × 4 true experimental design.MethodForty participants were randomly assigned to either the exercise or control groups and completed the Tower of London task prior to, immediately following, 30 min after, and 60 min after cessation of a 30 min, moderate intensity cycling exercise.ResultsAcute exercise positively impacted the total move score, which reflects planning efficiency, immediately after the cessation of exercise. Acute exercise also led to longer total initiation times, which were linked to better response inhibition of planning at 30 and 60 min after the cessation of exercise.ConclusionAcute exercise benefits planning, and the types of planning and the time points at which they were assessed modulate the relationship between acute exercise and executive function. Exercise-induced physiological and biological fluctuations have been proposed to explain the effects present immediately after exercise, and the mechanisms of such effects warrant further exploration.     

Conjunctive representations in learning and memory: principles of cortical and hippocampal function

The authors present a theoretical framework for understanding the roles of the hippocampus and neocortex in learning and memory. This framework incorporates a theme found in many theories of hippocampal function: that the hippocampus is responsible for developing conjunctive representations binding together stimulus elements into a unitary representation that can later be recalled from partial input cues. This idea is contradicted by the fact that hippocampally lesioned rats can learn nonlinear discrimination problems that require conjunctive representations. The authors' framework accommodates this finding by establishing a principled division of labor, where the cortex is responsible for slow learning that integrates over multiple experiences to extract generalities whereas the hippocampus performs rapid learning of the arbitrary contents of individual experiences. This framework suggests that tasks involving rapid, incidental conjunctive learning are better tests of hippocampal function. The authors implement this framework in a computational neural network model and show that it can account for a wide range of data in animal learning.     

Universality and context-specificity in early executive function development

A renewed interest in early executive function (i.e., EF or the conscious control of thought and behavior) development has led several research groups to suggest that EF may be emerging and is less coordinated (e.g., showing few relations between tasks) in the first few years (Devine et al., 2019; Gago Galvagno et al., 2021; Johansson et al., 2016; Miller & Marcovitch, 2015; Ribner et al., 2022). This potentially universal development in EF does not exclude the possibility that EF may also differ across context (e.g., Gago Galvagno et al., 2021; Lohndorf et al., 2019; Tran et al., 2015) reflecting unique strengths and development built within one’s sociocultural environment. The present paper explores potential universal and context-specific early EF developments by focusing on three aims: (1) reviewing work on EF within the first two years of life that may speak to potential universality in the measurement, structure, growth, stability, and conceptualization of early EF (2) reviewing research that may speak to how the sociocultural context may play a role in context-specific development within early EF and (3) examining potential developmental EF frameworks for understanding universal and context-specific developments of early EF within context.     

Contrasting Grammatical and Lexical Determiners

This paper investigates the difference between the production of grammatical determiners and lexical determiners in the production of adjective-noun phrases (NPs) in Danish. Models of sentence processing (Garrett in Psychology of learning and motivation, Academic press, New York, pp 133–177, 1975; Bock in J Mem Lang 26(2):119–137, 1987) suggest that the phonological encoding stage of grammatical items can only be specified once lexical items have been phonologically encoded. In their usage-based linguistic theory of the grammar-lexicon distinction, Boye and Harder (Lang 88(1):1–44, 2012) propose that this later encoding of grammatical elements is motivated by two specific features of grammatical elements. The first feature, dependence, is that grammatical items (morphemes, words, constructions) cannot be produced in isolation, but are always dependent on a lexical host item. This feature entails a more complex processing which might lead to longer reaction times when comparing the production of NPs with a grammatical determiner to a lexical one. Additionally, a more complex processing might lead to a lower accuracy rate for the grammatical condition relative to the lexical one. The second feature, low prominence, is that grammatical items code background information and therefore cannot convey the main point of a linguistic message. Less focus on grammatical elements might lead to a lower accuracy rate for the production of grammatical elements relative to lexical ones. Those predictions were tested in a task comparing the production of Danish grammatical determiners (indefinite articles) with the production of lexical ones (numerals, which are homonymous with the articles except for a stress difference) in similar contexts. Group-based analyses were performed in order to take inter-individual differences into account. The results show that the two features as proposed by Boye and Harder (2012) are only revealed for the fastest speakers group but not the slower ones.     

Contrasting reduced overshadowing and blocking

Preexposure of a cue without an outcome (X-) prior to compound pairings with the outcome (XZ-->O) can reduce overshadowing of a target cue (Z). Moreover, pairing a cue with an outcome (X-->O) before compound training can enhance its ability to compete with another cue (i.e., blocking). Four experiments were conducted in a conditioned bar-press suppression preparation with rats to determine whether spacing of the X- or X-->O trials would differentially affect reduced overshadowing and blocking. Experiment 1a showed that reduced overshadowing was larger with massed trials than with spaced trials. Experiment 1b found that blocking was larger with spaced trials than with massed trials. Experiments 2a and 2b indicated that these effects of trial spacing were both mediated by the associative status of the context at test. The results are interpreted in the framework of contemporary learning theories.     

Dynamic shifts in corticostriatal expression patterns of the immediate early genes Homer 1a and Zif268 during early and late phases of instrumental training

Adaptive motor actions require prior knowledge of instrumental contingencies. With practice, these actions can become highly automatic in nature. However, the molecular and anatomical substrates mediating these related forms of learning are not understood. In the present study, we used in situ hybridization to measure the mRNA levels of two immediate early genes (IEGs) in an instrumental paradigm where rats learned to lever-press for food. We report that after three training sessions, Homer 1a and Zif268 (an effector and regulatory IEG, respectively) were significantly induced within an extensive corticostriatal network relative to untrained controls. With extended training (23 sessions), however, a shift in the expression patterns of the two genes was evident. Expression of Homer 1a (official symbol Homer1) decreased significantly in frontal and cingulate cortices, whereas striatal expression was generally maintained. Interestingly, Homer 1a expression markedly increased with extensive training in the ventrolateral region of the striatum (VLS) relative to early learners, suggesting that plasticity in the VLS is required for the efficient production of the learned behavior or in habit formation. Zif268 (official symbol Egr1) expression generally decreased with extensive training; however, these changes were not significant. These results demonstrate for the first time, on a molecular level, a dynamic shift in the contribution of corticostriatal systems mediating the early acquisition and consolidation of goal-directed responses to those engaged after extensive training.     

Contrasting conceptions of perception and action

An examination of contrasting conceptions of perceptual processes, control of action and the nature of the linkage between perception and action leads to identification of a family of options. Two of these options, labeled pure realism and pure constructivism, are widely recognized. The argument is offered that the other options, which are hybrid networks of propositions, cannot be ruled out on a priori grounds. Nevertheless, the hybrids are usually ignored. It is proposed that investigators in the field of perception and action should embark on programmatic research that evaluates these contrasting conceptions on common empirical terrain.