Anterior Prefrontal Involvement in Implicit Contextual Change Detection

Anterior prefrontal cortex is usually associated with high level executive functions. Here, we show that the frontal pole, specifically left lateral frontopolar cortex, is involved in signaling change in implicitly learned spatial contexts, in the absence of conscious change detection. In a variant of the contextual cueing paradigm, participants first learned contingencies between distractor contexts and target locations implicitly. After learning, repeated distractor contexts were paired with new target locations. Left lateral frontopolar [Brodmann area (BA) 10] and superior frontal (BA9) cortices showed selective signal increase for this target location change in repeated displays in an event-related fMRI experiment, which was most pronounced in participants with high contextual facilitation before the change. The data support the view that left lateral frontopolar cortex is involved in signaling contextual change to posterior brain areas as a precondition for adaptive changes of attentional resource allocation. This signaling occurs in the absence of awareness of learned contingencies or contextual change

Repeated Contextual Search Cues Lead to Reduced BOLD-Onset Times in Early Visual and Left Inferior Frontal Cortex

Repetition of context can facilitate search for targets in distractor-filled displays. This contextual cueing goes along with enhanced event-related brain potentials in visual cortex, as previously demonstrated with depth electrodes in the human brain. However, modulation of the BOLD-response in striate and peristriate cortices has, to our knowledge, not yet been reported as a consequence of contextual cueing. Here, we report a selective reduction of the BOLD onset latency for repeated distractor configurations in these areas. In addition, the same onset latency reduction was observed in posterior inferior frontal cortex, a potential source area for feedback signals to early visual areas

Single-Trial Characterization of BOLD fMRI Responses by Self-Organizing Neural Networks

Functional magnetic resonance imaging (fMRI) plays a dominant role in human brain mapping studies. As of today, no standards exist for processing fMRI data and analysis techniques are often associated to the different stimulation paradigms used to acquire functional data. Being able to estimate the hemodynamic response following a single execution of a task permits to characterize its relationship to different aspects of the stimulus, and of the subject’s performance. This works is aimed to test a strategy for the characterization of single trial-related BOLD fMRI responses based on the self-organizing maps method of Kohonen (SOMs). Analysis have been carried out on synthetic fMRI images modeling activation and on data from a single-event fMRI experiment on one human subject performing a basic motor task. Results were able to define the potentiality range for this data-driven methodology in monitoring the evolution of the BOLD response deriving from a single stimulation

An ARX model-based approach to trial by trial identification of fMRI-BOLD responses

Being able to estimate the fMRI-BOLD response following a single task or stimulus is certainly of value, since it allows to characterize its relationship to different aspects either of the stimulus, or of the subject's performance. In order to detect and characterize BOLD responses in single trials, we developed and validated a procedure based on an AutoRegressive model with eXogenous Input (ARX). The use of an individual exogenous input for each voxel makes the modeling sensitive enough to reveal differences across regions, avoiding any a priori assumption about the reference signal. The detection of variability across trials is ensured by a suitable choice, for each voxel, of the order of the moving average, which in our implementation determines the relative delay between the recorded and the reference signal. This is a quality useful in finding different time profiles of activation from high temporal resolution fMRI data. The results obtained from simulated fMRI data resulting from synthetic activations in actual noise indicate that such approach allows to evaluate important features of the response, such as the time to onset, and time to peak. Moreover, the results obtained from real high temporal resolution fMRI data acquired at l.5 T during a motor task are consistent with previous knowledge about the responses of different cortical areas in motor programming and execution. The proposed procedure should also prove useful as a pre-processing step in different approaches to the analysis of fMRI data

Analisi di dati fMRI-BOLD a singolo evento: un approccio con reti neurali non supervisionate

Negli studi di risonanza magnetica funzionale (fMRI) cerebrale hanno assunto particolare rilevanza i protocolli di stimolazione basati su singoli eventi. Nel lavoro viene descritta una strategia di analisi di dati fMRI-BOLD, con lo scopo di rilevare il profilo temporale della risposta ad ogni singola stimolazione, nelle diverse aree cerebrali coinvolte. Il metodo si avvale di una fase di pre-elaborazione dei dati finalizzata ad incrementare il basso contrasto segnale-rumore tipico di dati derivanti da un singolo evento e di una fase di classificazione, caratterizzazione e localizzazione delle risposte realizzata implementando una rete neurale basata sull\u2019algoritmo di Kohonen delle mappe auto-organizzanti (SOMs). I risultati, ottenuti sia su immagini fMRI simulate, che su dati reali relativi ad un soggetto umano, mostrano la validita\u2019 di questo approccio guidato dai dati nell\u2019identificazione delle risposte ad una singola stimolazione e ne forniscono i limiti di applicabilita\u2019

Simultaneous acquisition of time-domain fNIRS and fMRI during motor activity

A time-domain fNIRS system was developed for simultaneous acquisition with fMRI. Preliminary results during motor activity indicate good sensitivity and temporal resolution of the system. To our knowledge this is the first time-domain fNIRS and fMRI study on human brain

High Occurrence of Methicillin-Resistant Staphylococcus aureus in Horses at Slaughterhouses Compared with Those for Recreational Activities: A Professional and Food Safety Concern?

The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in horses and its zoonotic potential is poorly understood. The objective of this study is to provide data on the prevalence and genetic characteristics of MRSA isolated from horses on farms, at racecourses, and at slaughterhouses in Italy, using standard and molecular methods. In addition, we report the prevalence of MRSA in horse handlers. Among 388 horses tested by nasal swabs, 27 (7%) were positive for MRSA ST398 (t011, t899, t1255) and ST1 (t127). The prevalence of MRSA in horses tested at slaughterhouses was significantly higher ( p < 0.001) compared with those tested on farms and racecourses. Five (7%) out of 67 staff members working in close contact with horses (2 from slaughterhouse, 2 from riding stable, and 1 from racecourse) were carriers of MRSA ST398 (t011, t034) and ST1 (t127). The isolates from horses and humans carried SCCmec IVa or V and were pvl negative and pia positive. All the isolates from both horses and humans were resistant to at least two antimicrobial classes. The circulation of MRSA in horses and in humans working in close contact with them should be considered an emerging public health issue. In fact, it represents a potential risk for people who work in close contact with horses, and for horse meat consumers