Successful communication between two people depends first on the recognition of the intention to communicate. Such intentions may be conveyed by signals directed at the self, such as calling a person's name or making eye contact. In this study we use functional magnetic resonance imaging to show that the perception of these two signals, which differ in modality and sensory channel, activate common brain regions: the paracingulate cortex and temporal poles bilaterally. These regions are part of a network that has been consistently activated when people are asked to think about the mental states of others. Activation of this network is independent of arousal as measured by changes in pupil diameter.

Faces are visual objects in our environment that provide strong social cues, with the eyes assuming particular importance. Here we show that the perceived attractiveness of an unfamiliar face increases brain activity in the ventral striatum of the viewer when meeting the person's eye, and decreases activity when eye gaze is directed away. Depending on the direction of gaze, attractiveness can thus activate dopaminergic regions that are strongly linked to reward prediction, indicating that central reward systems may be engaged during the initiation of social interactions.

Musically naive participants were scanned before and after a period of 15 weeks during which they were taught to read music and play the keyboard. When participants played melodies from musical notation after training, activation was seen in a cluster of voxels within the bilateral superior parietal cortex. A subset of these voxels were activated in a second experiment in which musical notation was present, but irrelevant for task performance. These activations suggest that music reading involves the automatic sensorimotor translation of a spatial code (written music) into a series of motor responses (keypresses).

SUMMARY1. Voltage-dependent potassium channels were investigated in rat axonal membrane by means of the patch-clamp recording technique. Three different types of channels (F, I and S) have been characterized on the basis of their single-channel conductance, activation, deactivation and inactivation properties.2. The fast (F) channels were activated smoothly at potentials (E) between -50 and 50 mV (E50 = 4-6 mV). They had a conductance of 55 pS for inward current and 30 pS for outward current in solutions containing 155 mm K+ (high K+) on both sides of the membrane at 21-23 'C. The F-channels demonstrated the fastest deactivation, within 1-2 ms, and inactivated in a few hundreds of milliseconds. The time constant of inactivation was 143 ms at E = +40 mV.3. The intermediate (I) channels activated steeply between E =-70 and -50 mV (E50 = -64-2 mv) and had a single-channel conductance of 33 pS for inward and 18 ps for outward currents. The I-channels deactivated with intermediate kinetics with the time constants of 20-4 ms and 10-1 ms at E = -80 mV and E = -100 mV, respectively. Complete inactivation of the channels developed over tens of seconds. The time constant of inactivation was 7-4 s at E = + 40 mV.4. The slow (S) channels were active at potentials positive to -90 mV. Their conductance was 10 pS for inward currents. The time constant of activation of the S-channels was strongly potential dependent. At a holding potential of -100 mV the channels deactivated during a long time interval between 30 ms and 1 s, producing long-lasting tail currents. The mean time constant of deactivation for S-channels was 129 ms.5. The conductances of F-and I-channels measured under normal physiological conditions (Ringer solution in bath) were 17 and 10 pS, respectively. 6. Tetraethylammonium (TEA), the classic blocker of potassium channels, suppressed F-, I-and

The distribution of glutamate receptor subtypes on the surface of neurons is highly relevant for synaptic activation and signal processing in the neocortex. As a novel approach we have used infra-red videomicroscopy in combination with photostimulation or microiontophoresis in brain slices of rat neocortex to map the distribution of N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors on pyramidal neurons of layer V. Both modes of application revealed a spatially distinct distribution of glutamate receptor subtypes: the soma and the proximal dendrite of neurons are highly sensitive to NMDA, whereas the more distal parts of the dendrite are more sensitive to AMPA. An implication is that NMDA receptors near the soma might regulate the amplification of synaptic signals resulting from AMPA receptor activation on remote dendritic sites.

Localizing sensorimotor areas with high resolution functional MRI is of considerable interest for a wide range of medical applications from the preoperative planning of neurosurgical interventions to determining the course of neuroplastic reorganisation after brain lesions. We examined the effect of the stimulation frequency on the blood oxygen level dependent (BOLD) fMRI response and on perfusion weighted fMRI using electrical median nerve stimulation at 5, 15, 40, and 100 Hz. BOLD fMRI was performed using a single shot gradient echo EPI sequence to acquire 15 contiguous slices. For the qualitative flow sensitive studies, a single slice inversion recovery prepared spin echo echoplanar sequence (IR-SE EPI) was used. In the primary sensorimotor cortex, a linear increase of the fMRI-BOLD response, affecting both the number of activated pixels and the amplitude of the signal changes, was seen with increasing stimulation frequencies. The qualitative in-flow sensitive studies, using the IR-SE EPI sequence, indicate that the tissue perfusion also increases over the same range of frequencies. This implicates that larger fMRI responses can be obtained if electrical median nerve stimulation is performed at higher frequencies. The results are compared with electrophysiological data, which show a decrease of the early somatosensory evoked potentials at higher frequencies.

Two types of metabolically regulated K channels have been identified for the first time in enzymatically demyelinated fibres of amphibian sciatic nerve using the patch-clamp technique. A maxi K channel with a single-channel conductance of 132 pS (105 mM K on both sides of the membrane, 15 degrees C) is activated both by micromolar concentrations of internal Ca and by depolarization. A second type of K channel with a conductance of 44 pS is inhibited by intracellular adenosine 5'-triphosphate (ATP) with a half-maximal inhibitory concentration (IC50) of 35 microM. It is blocked by submicromolar concentrations of external glibenclamide. Both channels are sensitive to external tetraethylammonium chloride (IC50 = 0.2 mM for the maxi K channel and 4.2 mM for the ATP-sensitive channel). They may be part of a complex feedback system regulating axonal excitability under various metabolic conditions.

Although the relative potency measured by the number of units per nanogram of the toxin is different for the three preparations (BOTOX = 20 U/ng; Dysport = 40 U/ng, and CS-BOT = 15.2 U/ng), the effective dose for CS-BOT is similar to that of BOTOX (Allergan, Irvine, CA). Despite the twofold difference in potency per nanogram, it appears that the clinically observable activity of 1 U of BOTOX is roughly equivalent to 3 U of the Dysport (Inamed, Santa Barbara, CA) product. Using quantitative analysis of regional paralysis produced by local injections into the gastrocnemius muscles of mice, prior studies estimated the potency ratio between Dysport and BOTOX to be 4.2 to 1. In a single-blind, randomized comparison study of Dysport and BOTOX in 91 patients with blepharospasm or hemifacial spasm, it was found that 4:1 dose ratio produced similar benefits. A similar 4:1 Dysport:BOTOX ratio was found to produce equivalent beneficial effects in a double-blind study in patients with blepharospasm, but the frequency of side effects, particularly of ptosis, was lower in the BOTOX group. In a study of 73 patients with cervical dystonia treated either with Dysport or BOTOX, it was concluded that a 3:1 ratio provides equivalent results. But a recent study concluded that the appropriate conversion factor between BOTOX and Dysport is less than 3. Therefore, there is some controversy about the relative potencies of the two preparations, with one study proposing that 1 unit of BOTOX corresponds to 1 unit of Dysport.