Emergence of synaptic organization and computation in dendrites

Single neurons in the brain exhibit astounding computational capabilities, which gradually emerge throughout development and enable them to become integrated into complex neural circuits. These capabilities derive in part from the precise arrangement of synaptic inputs on the neurons' dendrites. While the full computational benefits of this arrangement are still unknown, a picture emerges in which synapses organize according to their functional properties across multiple spatial scales. In particular, on the local scale (tens of microns), excitatory synaptic inputs tend to form clusters according to their functional similarity, whereas on the scale of individual dendrites or the entire tree, synaptic inputs exhibit dendritic maps where excitatory synapse function varies smoothly with location on the tree. The development of this organization is supported by inhibitory synapses, which are carefully interleaved with excitatory synapses and can flexibly modulate activity and plasticity of excitatory synapses. Here, we summarize recent experimental and theoretical research on the developmental emergence of this synaptic organization and its impact on neural computations.

Emergence of local and global synaptic organization on cortical dendrites

Synaptic inputs on cortical dendrites are organized with remarkable subcellular precision at the micron level. This organization emerges during early postnatal development through patterned spontaneous activity and manifests both locally where nearby synapses are significantly correlated, and globally with distance to the soma. We propose a biophysically motivated synaptic plasticity model to dissect the mechanistic origins of this organization during development and elucidate synaptic clustering of different stimulus features in the adult. Our model captures local clustering of orientation in ferret and receptive field overlap in mouse visual cortex based on the receptive field diameter and the cortical magnification of visual space. Including action potential back-propagation explains branch clustering heterogeneity in the ferret and produces a global retinotopy gradient from soma to dendrite in the mouse. Therefore, by combining activity-dependent synaptic competition and species-specific receptive fields, our framework explains different aspects of synaptic organization regarding stimulus features and spatial scales.

Adaptation of spontaneous activity in the developing visual cortex

Spontaneous activity drives the establishment of appropriate connectivity in different circuits during brain development. In the mouse primary visual cortex, two distinct patterns of spontaneous activity occur before vision onset: local low-synchronicity events originating in the retina and global high-synchronicity events originating in the cortex. We sought to determine the contribution of these activity patterns to jointly organize network connectivity through different activity-dependent plasticity rules. We postulated that local events shape cortical input selectivity and topography, while global events homeostatically regulate connection strength. However, to generate robust selectivity, we found that global events should adapt their amplitude to the history of preceding cortical activation. We confirmed this prediction by analyzing in vivo spontaneous cortical activity. The predicted adaptation leads to the sparsification of spontaneous activity on a slower timescale during development, demonstrating the remarkable capacity of the developing sensory cortex to acquire sensitivity to visual inputs after eye-opening.

Oxytocin Shapes Spontaneous Activity Patterns in the Developing Visual Cortex by Activating Somatostatin Interneurons

Spontaneous network activity shapes emerging neuronal circuits during early brain development prior to sensory perception. However, how neuromodulation influences this activity is not fully understood. Here, we report that the neuromodulator oxytocin differentially shapes spontaneous activity patterns across sensory cortices. In vivo, oxytocin strongly decreased the frequency and pairwise correlations of spontaneous activity events in the primary visual cortex (V1), but it did not affect the frequency of spontaneous network events in the somatosensory cortex (S1). Patch-clamp recordings in slices and RNAscope showed that oxytocin affects S1 excitatory and inhibitory neurons similarly, whereas in V1, oxytocin targets only inhibitory neurons. Somatostatin-positive (SST+) interneurons expressed the oxytocin receptor and were activated by oxytocin in V1. Accordingly, pharmacogenetic silencing of V1 SST+ interneurons fully blocked oxytocin's effect on inhibition in vitro as well its effect on spontaneous activity patterns in vivo. Thus, oxytocin decreases the excitatory/inhibitory (E/I) ratio by recruiting SST+ interneurons and modulates specific features of V1 spontaneous activity patterns that are crucial for the wiring and refining of developing sensory circuits.

Negative effects of psychotherapy: a missing piece

Through the case history method this study examines one neglected phenomenon of negative effects—the negative effect which relapses or is actually positive. The relationship of this type of negative effect to the evaluation, of therapy and to the therapeutic process is explored.

Personality of alcoholics as measured by Sixteen Personality Factor Questionnaire and House-Tree-Person color-choice characteristics

This report describes four studies of measures of the alcoholic personality by the Sixteen Personality Factor Questionnaire and the House-Tree-Person. In a sample of 49 male alcoholics support was found for the 16 PF alcoholic personality reported in earlier studies on 4 to 7 scales. Differences in incidence of 20 chromatic characteristics of drawings and in sex of the HTP person drawings between normals and alcoholics were also discovered. Previous research on collegiates reported some low but significant point biserial correlations and discriminant functions between 16 PF traits and trait combinations, and 20 chromatic drawing characteristics. In three instances, alcoholic and college men's drawing characteristics correlated significantly ( p < .05) with the same 16 PF scale. In three other cases, identical findings occurred in correlations of alcoholic men and college women's drawings and traits. Comparison of the data from alcoholics and college students led to the conclusion that in general relationships between drawing characteristics and personality traits may well depend on the type of sample used. Suggestions for further research were made.

The HTP weeping willow and personality traits

Comparison of 16 PF scores of 12 college students who drew weeping willow trees, when matched with those of 12 others for sex, age, and college class, did not support the hypothesis suggested by the literature that drawers of weeping willows would score lower on Factor F (Sober—Happy-go-lucky).

I-dots in the handwriting of a clinical sample

Handwriting of 40 alcoholic and 32 schizophrenic hospital patients was examined for consistency or omission of i-dots. It was hypothesized that the hospital group would show the same personality characteristics on two scales of the 16 PF that occurred in previous research with 103 college students. Results were significant but in the opposite direction. Reasons for the differences in these findings were discussed.