Topology of local information dynamics during motor decision in the premotor cortex of primates

Complex systems are very large systems comprising millions of agents interacting with each other and whose collective behaviour cannot be understood from the elementary features. In this sense the brain is the complex system par excellence: hundreds of billions of densely packed electrically excitable cells called neurons with hundred of millions of connections each. All exchanging electrochemical signals over short and long distances every few milliseconds and functionally interacting over multiple scales of time. Within this apparent chaotic bundle some deep questions arise. A single neuron is not in itself "intelligent" but a vast network of neurons can think, perceive, remember and generate the many extraordinary phenomena that they are collectively known as mind. How the mind can emerge from the interconnection between different neurons? How can single interactions between neurons organize themselves into manifestations collectively coherent like perception and movement

Hierarchical organization of functional connectivity in the mouse brain: a complex network approach

This paper represents a contribution to the study of the brain functional connectivity from the perspective of complex networks theory. More specifically, we apply graph theoretical analyses to provide evidence of the modular structure of the mouse brain and to shed light on its hierarchical organization. We propose a novel percolation analysis and we apply our approach to the analysis of a resting-state functional MRI data set from 41 mice. This approach reveals a robust hierarchical structure of modules persistent across different subjects. Importantly, we test this approach against a statistical benchmark (or null model) which constrains only the distributions of empirical correlations. Our results unambiguously show that the hierarchical character of the mouse brain modular structure is not trivially encoded into this lower-order constraint. Finally, we investigate the modular structure of the mouse brain by computing the Minimal Spanning Forest, a technique that identifies subnetworks characterized by the strongest internal correlations. This approach represents a faster alternative to other community detection methods and provides a means to rank modules on the basis of the strength of their internal edges.Comment: 11 pages, 9 figure

The small scale functional topology of movement control: Hierarchical organization of local activity anticipates movement generation in the premotor cortex of primates.

How neurons coordinate their collective activity for behavioural control is an open question in neuroscience. Several studies have progressively proven, on various scales, that the patterns of neural synchronization change accordingly with behavioural events. However, the topological features of the neural dynamics that underlie task-based cognitive decisions on the small scale level are not understood. We analysed the multiunit activity (MUA) from a multielectrode (96 channels) array of the dorsal premotor cortex (PMd) in rhesus monkeys during a countermanding reaching task. Within the framework of graph theory, we found that in the local PMd network motor execution is preceded by the emergence of hubs of anti-correlation that are organized in a hierarchical manner. Conversely, this organization is absent when monkeys correctly inhibit programmed movements. Thus, we interpret the presence of hubs as reflecting the readiness of the motor plan and the irrevocable signature of the onset of the incoming movement

The premises of a transitive inference task modulate the synchrony of local field potentials in macaque dorsal premoto rcortex

Transitive reasoning is a high-level cognitive ability allowing the prediction of novel knowledge by linking previously acquiredinformation. To study this ability in experimental settings participants are required first to acquire a set of premises for an inferential deduction as A>B, B>C, C>D, D>E, or E>F (Learning phase), and then to identify the ordinal relationship between two items notembedded in the premises as infer that B>E (Test phase). Several brain imaging studies in humans highlighted which cortical and subcortical areas are recruited during the execution of the different steps of this Transitive Inference (TI) task (Xiaoyinget al., 2022). Recently monkey neurophysiology studies approached the investigation of the neuronal computations subtending this ability and observed that the activity of premotor cortex is modulated by the difficulty in comparing items during the test phase. If and how the activity of this area is modulated by the acquisition of the premises of this task is an open question. Here we investigated if this acquisition is reflected in the modulation of the local field potential (LFP)

Neuronal population dynamics and network organizations reflect motivational context in monkey premotor cortex during movement execution and inhibition

Actions require constant updating of response preparation, which may involve suppressing or executing the action depending on context. Many studies have shown that the dorsal premotor cortex (PMd) is a key area for controlling the level of movement preparation. However, it is still unclear how contextual information is integrated to regulate movement preparation. To address this issue, we investigated the neuronal population dynamics and network organization in different motivational contexts. We recorded neuronal activity from PMd of two monkeys (Macaca mulatta), performing a a stop-signal reaching task. The task required to respond to a Go signal as fast as possible (Go trials), and to inhibit the response if an unexpected Stop signal (Stop trial) was presented. Before each trial, a Cue signal indicated in which motivational context (Go+: higher reward for correct Go than Stop trials; Stop+: higher reward for Stop than Go trials; Neutral: same amount for both correct trials) the current trial would run. We used spike density function (SDF) to perform neuronal analysis on well-isolated single unit activity. We extracted the neuronal dynamic by mapping the neuronal population activity in a Low-Dimensional State Space using a Principal Component Analysis (PCA). We also investigated the multiscale network topology by using the node-based multifractal analysis framework (NMFA) and minimal spanning tree analysis (MST). Behavioral results show that in both animals (M1 sessions=2; M2 sessions=5) the motivational context affected motor preparation by lengthening response times (RT) and increasing the ability to inhibit in the Stop+ condition compared to the Go+ condition. Analysis of the neuronal state space showed that in Go trials of the Stop+ and Neutral conditions, the neural trajectories from the Go signal to motion generation evolved similarly, while in the Go+ condition, the trajectories followed a different evolution. The functional network analysis revealed that PMd has a more complex organization when deciding to stop than when deciding to move in the Go+ condition. However, this difference in complexity wasn’t present in the Stop+ and Neutral conditions. The MST identified the topological backbone of the network revealing a network endowed have with hubs present the Go+ condition in both trial types, absent in the other conditions with a more dispersed functional communication between neurons. These results indicate that the motivational context influences the movement preparation in PMd. At neuronal level, these influences can be detected as changes in the neuronal dynamics, as well as in the complexity and topological organization of the network

Functional network complexity reflects diverse reward contexts in macaque premotor cortex

The behavior in the stop signal task-probing inhibitory control-is strongly modulated by the reward context, and this modulation is reflected in neural activity recorded from single sites of the dorsal premotor cortex (PMd) of macaque monkeys [1]. However, how the neural dynamics of motor inhibition is modulated at the network level in different motivational contexts is still unexplored. To tackle the issue, we characterized the synchronization patterns between spiking activities (SUA) recorded using a multielectrode (Utah array, 96 electrodes) and applied graph theory methods to describe and quantify the complexity and heterogeneity of the network structure at different scales when movement is planned or successfully canceled after the presentation of a Stop signal

Reward prospect affects strategic adjustments in stop signal task

Interaction with the environment requires us to predict the potential reward that will follow our choices. Rewards could change depending on the context and our behavior adapts accordingly. Previous studies have shown that, depending on reward regimes, actions can be facilitated (i.e., increasing the reward for response) or interfered (i.e., increasing the reward for suppression). Here we studied how the change in reward perspective can influence subjects’ adaptation strategy. Students were asked to perform a modified version of the Stop-Signal task. Specifically, at the beginning of each trial, a Cue Signal informed subjects of the value of the reward they would receive; in one condition, Go Trials were rewarded more than Stop Trials, in another, Stop Trials were rewarded more than Go Trials, and in the last, both trials were rewarded equally. Subjects participated in a virtual competition, and the reward consisted of points to be earned to climb the leaderboard and win (as in a video game contest). The sum of points earned was updated with each trial. After a learning phase in which the three conditions were presented separately, each subject performed 600 trials testing phase in which the three conditions were randomly mixed. Based on the previous studies, we hypothesized that subjects could employ different strategies to perform the task, including modulating inhibition efficiency, adjusting response speed, or employing a constant behavior across contexts. We found that to perform the task, subjects preferentially employed a strategy-related speed of response adjustment, while the duration of the inhibition process did not change significantly across the conditions. The investigation of strategic motor adjustments to reward’s prospect is relevant not only to understanding how action control is typically regulated, but also to work on various groups of patients who exhibit cognitive control deficits, suggesting that the ability to inhibit can be modulated by employing reward prospects as motivational factors

White Paper of Italian Gastroenterology: Delivery of services for digestive diseases in Italy: Weaknesses and strengths

In 2011 the three major Italian gastroenterological scientific societies (AIGO, the Italian Society of Hospital Gastroenterologists and Endoscopists; SIED, the Italian Society of Endoscopy; SIGE, the Italian Society of Gastroenterology) prepared their official document aimed at analysing medical care for digestive diseases in Italy, on the basis of national and regional data (Health Ministry and Lombardia, Veneto, Emilia-Romagna databases) and to make proposals for planning of care. Digestive diseases were the first or second cause of hospitalizations in Italy in 1999-2009, with more than 1,500,000 admissions/year; however only 5-9% of these admissions was in specialized Gastroenterology units. Reported data show a better outcome in Gastroenterology Units than in non-specialized units: shorter average length of stay, in particular for admissions with ICD-9-CM codes proxying for emergency conditions (6.7 days versus 8.4 days); better case mix (higher average diagnosis-related groups weight in Gastroenterology Units: 1 vs 0.97 in Internal Medicine units and 0.76 in Surgery units); lower inappropriateness of admissions (16-25% versus 29-87%); lower in-hospital mortality in urgent admissions (2.2% versus 5.1%); for patients with urgent admissions due to gastrointestinnal haemorrhage, in-hospital mortality was 2.3% in Gastroenterology units versus 4.0% in others. The present document summarizes the scientific societies' official report, which constitutes the "White paper of Italian Gastroenterology". © 2014 Editrice Gastroenterologica Italiana S.r.l