Understanding the concept of a novel tool requires interaction of the dorsal and ventral streams.

The left hemisphere tool-use network consists of the dorso-dorsal, ventro-dorsal, and ventral streams, each with distinct computational abilities. In the dual-loop model, the ventral pathway through the extreme capsule is associated with conceptual understanding. We performed a learning experiment with fMRI to investigate how these streams interact when confronted with novel tools. In session one, subjects observed pictures and video sequences in real world action of known and unknown tools and were asked whether they knew the tools and whether they understood their function. In session two, video sequences of unknown tools were presented again, followed again by the question of understanding their function. Different conditions were compared to each other and effective connectivity (EC) in the tool-use network was examined. During concept acquisition of an unknown tool, EC between dorsal and ventral streams was found posterior in fusiform gyrus and anterior in inferior frontal gyrus, with a functional interaction between BA44d and BA45. When previously unknown tools were presented for a second time, EC was prominent only between dorsal stream areas. Understanding the concept of a novel tool requires an interaction of the ventral stream with the dorsal streams. Once the concept is acquired, dorsal stream areas are sufficient.

Accelerated brain ageing in sepsis survivors with cognitive long-term impairment.

In the last years, cognitive impairment was emphasized to be a prominent long-term sequelae of sepsis. The level of cognitive impairment is comparable with that in mild cognitive impairment (MCI) patients. Whether sepsis survivors also show a comparable brain atrophy is still unclear. For the analysis of brain atrophy, a novel method named brain age gap estimation (BrainAGE) was used. In this analysis approach, an algorithm identifies age-specific atrophy across the whole brain and calculates a BrainAGE score in years. In case of accelerated brain atrophy, the BrainAGE score is increased in comparison to the healthy age reference group, indicating a difference in estimated chronological age. 20 survivors of severe sepsis (longer than 2 years post sepsis) with persistent cognitive deficits were investigated with a battery of neuropsychological tests. Their MRI images were compared to an age- and sex-matched control group. Sepsis survivors showed a significant higher BrainAGE score of 4.5 years compared to healthy controls. We also found a close relationship between the BrainAGE score and severity of cognitive impairment (a higher BrainAGE score was associated with more severe cognitive impairment). Consequently, sepsis survivors with persistent cognitive impairment showed an accelerated brain ageing, which was closely associated with the severity of cognitive impairment (similar to MCI patients).

Boosting the Motor Outcome of the Untrained Hand by Action Observation: Mirror Visual Feedback, Video Therapy, or Both Combined-What Is More Effective?

Action observation (AO) allows access to a network that processes visuomotor and sensorimotor inputs and is believed to be involved in observational learning of motor skills. We conducted three consecutive experiments to examine the boosting effect of AO on the motor outcome of the untrained hand by either mirror visual feedback (MVF), video therapy (VT), or a combination of both. In the first experiment, healthy participants trained either with MVF or without mirror feedback while in the second experiment, participants either trained with VT or observed animal videos. In the third experiment, participants first observed video clips that were followed by either training with MVF or training without mirror feedback. The outcomes for the untrained hand were quantified by scores from five motor tasks. The results demonstrated that MVF and VT significantly increase the motor performance of the untrained hand by the use of AO. We found that MVF was the most effective approach to increase the performance of the target effector. On the contrary, the combination of MVF and VT turns out to be less effective looking from clinical perspective. The gathered results suggest that action-related motor competence with the untrained hand is acquired by both mirror-based and video-based AO.

Long-term sequelae of severe sepsis: cognitive impairment and structural brain alterations - an MRI study (LossCog MRI).

BACKGROUND: The number of patients with cognitive impairment after sepsis or septic shock is high. However, the underlying neurophysiological basis of sepsis induced cognitive impairment is not fully understood. METHODS/DESIGN: This is a prospective, controlled observational study. We are in the process of recruiting 25 survivors of severe sepsis or septic shock who will be investigated with functional MRI (fMRI), T1-weighted MRI und Diffusion Tensor Imaging (DTI) as well as Magnetoencephalography (MEG). Furthermore, patients will undergo neuropsychological evaluation using the DemTect and the clock drawing tests. In addition, verbal and declarative memory is assessed by the Verbal Learning and Memory Test. The primary aim is to determine the volumetry of the amygdala and the hippocampus. The secondary aim is to analyze the relationship between cognitive tests and MEG, and the (f)MRI results. Moreover, a between-group comparison will be evaluated to an age-matched group of healthy controls. DISCUSSION: In a previous MEG study, we observed a significant slowing of the prominent background activity in sepsis survivors and hepatic encephalopathy patients in particular shortly after discharge from the ICU. Intriguingly, the rhythmic brain activity after visual flickering stimulation was altered in sepsis survivors in comparison to age-matched healthy volunteers. We propose that this desynchronization is based on affected underlying neuronal responses between various interconnected brain regions. The current project will analyze whether the modifications are related to a damage of the fibers connecting different brain regions or to a disturbance of the functional interaction between different brain regions or even due to an atrophy of certain brain regions. TRIAL REGISTRATION: "Langzeitfolgen nach schwerer Sepsis: Kognitive Beeinträchtigungen und strukturelle Veränderungen am Gehirn, eine MRT Studie"; German Clinical Trials Register (DRKS00005484).

Association of activity changes in the primary sensory cortex with successful motor rehabilitation of the hand following stroke.

BACKGROUND: Previous studies demonstrated a posterior shift of activation toward the primary sensory cortex (S1) following stroke; however, any relationship between this posterior shift and clinical outcome measures for the affected hand function were unclear. OBJECTIVE: The authors investigated the possible role of S1 in motor recovery. METHODS: Assuming that previous studies examined inhomogeneous groups of patients, the authors selected participants with chronic stroke who had moderate hand paresis, normal sensory examination and somatosensory-evoked potentials, and no lesion within the S1, thalamus, or brain stem. Constraint-induced movement therapy (CIMT) was used to train the impaired hand. To relate fMRI (functional MRI) activation changes from baseline to post-CIMT, a correlation analysis was performed with changes of the Wolf Motor Function Test (WMFT) as a test for the hand function. RESULTS: A close relationship was found between increases in hand function and peak changes in activation within the ipsilesional S1. With a better outcome, greater increases in activation within the S1 were evident (P < .03; r = 0.73). CONCLUSION: In selected patients, the sensory network influences training-induced motor gains. This predictive knowledge of plasticity when applying CIMT may suggest strategies to enhance the effect of therapy, such as the addition of electrical stimulation to enhance S1 excitability.