Sensory attenuation, the top-down filtering or gating of afferent information, has been extensively studied in two fields: physiological and perceptual. Physiological sensory attenuation is represented as a decrease in the amplitude of the primary and secondary components of the somatosensory evoked potential (SEP) before and during movement. Perceptual sensory attenuation, described using the analogy of a persons' inability to tickle oneself, is a reduction in the perception of the afferent input of a self-produced tactile sensation due to the central cancellation of the reafferent signal by the efference copy of the motor command to produce the action. The fields investigating these two areas have remained isolated, so the relationship between them is unclear. The current study delivered median nerve stimulation to produce SEPs during a force-matching paradigm (used to quantify perceptual sensory attenuation) in healthy human subjects to determine whether SEP gating correlated with the behavior. Our results revealed that these two forms of attenuation have dissociable neurophysiological correlates and are likely functionally distinct, which has important implications for understanding neurological disorders in which one form of sensory attenuation but not the other is impaired. Time-frequency analyses revealed a negative correlation over sensorimotor cortex between gamma-oscillatory activity and the magnitude of perceptual sensory attenuation. This finding is consistent with the hypothesis that gamma-band power is related to prediction error and that this might underlie perceptual sensory attenuation.

Oscillatory activity in the beta frequency range from sensorimotor cortices is modulated by movement; however, the functional role of this activity remains unknown. In a recent study, Tan et al. tested a novel hypothesis that beta power reflects estimates of uncertainty in parameters of motor forward models.

The morphogenetic response of Brassica campestris genotype R500 to inhibitors of ethylene biosynthesis and action was investigated. A medium containing 1.0 mg.l(-1) NAA, 2.0 mg.l(-1) BAP, and 30 or 60 μM AgNO3 significantly enhanced both the percentage shoot regeneration and the number of shoots per cotyledon expiant. Although callus proliferation occurred on hypocotyl segments, no shoots were formed in response to AgNO3 with expiants older than five days. Cotyledons older than six days formed shoots only with AgNO3. Cobalt chloride at 20 and 30 μM increased cotyledon shoot regeneration but was inferior to AgNO3. Hypocotyl segments were unresponsive. Salicylic acid at 25 and 50 μM prevented both shoot regeneration and callusing without any obvious toxic effects. Removal of expiants from AgNO3 after 12 days did not alter the percentage of shoot regeneration but increased the number of shoots per expiant. This response was dependent on the level of BAP. Percentage shoot regeneration and number of shoots per cotyledon explant were not affected by removal of CoCl2. These results indicate that the poor regenerative capacity of this genotype may be related to ethylene biosynthesis or metabolism.

Interoception research is hampered by the lack of an agreed gold standard test of interoceptive accuracy. To avoid several confounds of heartbeat perception tasks, we devised a novel method of ‘heartbeat matching’, whereby participants use a custom-made slider to adjust the rate at which a heart icon is pulsing on a PC screen, to match this to the pace of their own heart. Because heartbeat counting has been shown to modulate with posture, participants completed both heartbeat matching and a standard heartbeat counting task while standing and when lying down. Accuracy was significantly higher in the heartbeat matching task. Moreover, ability to estimate elapsed time was also more accurate using the matching task but was not significantly correlated with interoceptive accuracy. Participants were more accurate on both tasks when lying down. However, participants underestimated the pace of their hearts in both methods. We discuss possible interpretations and how these might be distinguished.

It has been proposed that motor system activity during action observation may be modulated by the kinematics of observed actions. One purpose of this activity during action observation may be to predict the visual consequence of another person's action based on their movement kinematics. Here, we tested the hypothesis that the primary motor cortex (M1) may have a causal role in inferring information that is present in the kinematics of observed actions. Healthy participants completed an action perception task before and after applying continuous theta burst stimulation (cTBS) over left M1. A neurophysiological marker was used to quantify the extent of M1 disruption following cTBS and stratify our sample a priori to provide an internal control. We found that a disruption to M1 caused a reduction in an individual's sensitivity to interpret the kinematics of observed actions; the magnitude of suppression of motor excitability predicted this change in sensitivity.