Mechanisms underlying a thalamocortical transformation during active tactile sensation

During active somatosensation, neural signals expected from movement of the sensors are suppressed in the cortex, whereas information related to touch is enhanced. This tactile suppression underlies low-noise encoding of relevant tactile features and the brain’s ability to make fine tactile discriminations. Layer (L) 4 excitatory neurons in the barrel cortex, the major target of the somatosensory thalamus (VPM), respond to touch, but have low spike rates and low sensitivity to the movement of whiskers. Most neurons in VPM respond to touch and also show an increase in spike rate with whisker movement. Therefore, signals related to self-movement are suppressed in L4. Fast-spiking (FS) interneurons in L4 show similar dynamics to VPM neurons. Stimulation of halorhodopsin in FS interneurons causes a reduction in FS neuron activity and an increase in L4 excitatory neuron activity. This decrease of activity of L4 FS neurons contradicts the "paradoxical effect" predicted in networks stabilized by inhibition and in strongly-coupled networks. To explain these observations, we constructed a model of the L4 circuit, with connectivity constrained by in vitro measurements. The model explores the various synaptic conductance strengths for which L4 FS neurons actively suppress baseline and movement-related activity in layer 4 excitatory neurons. Feedforward inhibition, in concert with recurrent intracortical circuitry, produces tactile suppression. Synaptic delays in feedforward inhibition allow transmission of temporally brief volleys of activity associated with touch. Our model provides a mechanistic explanation of a behavior-related computation implemented by the thalamocortical circuit

Scientific Opinion on the effect on public or animal health or on the environment on the presence of seeds of Ambrosia spp. in animal feed

The European Commission requested EFSA to provide a scientific opinion on the effect on public or animal health or on the environment on the further distribution of Ambrosia spp. in the European Union and on the importance of feed materials, in particular bird feed, in the dispersion of Ambrosia spp. The genus Ambrosia (Asteraceae family) is distributed worldwide. Ambrosia artemisiifolia (common ragweed) has heavily colonised several areas of South-East Europe. Ambrosia spp., both in their native range and in invaded areas, are of public health concern due to the allergenic properties of their pollen. The NDA Panel concluded that inhalation of the plant pollen causes rhino-conjunctivitis and asthma, with skin allergies and food allergy playing minor roles. Ambrosia may cross-sensitize patients to other allergens, including food allergens. There is some evidence for allergenicity of Ambrosia pollen in animals. With regard to the effects on the environment of the further distribution of Ambrosia spp. in the European Union, the PLH Panel concluded that there is no direct evidence that Ambrosia spp. cause extinction of plant species. However, there are some indications that A. artemisiifolia could become highly invasive in certain environmentally-valuable habitats and might be linked to an impoverishment of species richness, therefore further ecological studies are needed. The CONTAM Panel focused on the relative importance of animal feed, bird feed in particular, on the dispersion of Ambrosia. Ambrosia seeds may contaminate feed. However, animal feed materials compounded for use in livestock are extensively processed. This processing destroys Ambrosia seeds and hence the contribution of compounded feed to the dispersion of Ambrosia is considered to be negligible. Bird feed often contains significant quantities of Ambrosia seeds and remains unprocessed. Therefore, bird feed seems to play an important role in introducing Ambrosia to new, previously not infested area