Ashley Mays | PubMed Health

PubMed2005

Lights can reverse illusory directional hearing.

Adding brief flashes of light to a train of auditory clicks [R. Hari, Illusory directional hearing in humans, Neurosci. Lett. 189 (1995) 29-30] can alter the sounds perceived location within the head. In an experimental procedure adopted from Hari [R. Hari, Illusory directional hearing in humans, Neurosci. Lett. 189 (1995) 29-30], 16 observers listened over headphones to 8 binaural clicks (i.e., 4 left-ear leading followed by 4 right-ear leading) separated by one of three ISIs (8, 64 and 120 ms), then reported the perceived location of each click-pair within the head. Flashing a light rightward across a CRT screen during temporally coincident click-pairs made observers report the location of the sounds in roughly equally spaced steps from left-to-right through the head. In contrast, light flashes originating on the right of the CRT and moving leftward reversed the perceived location of the clicks, so that the sound appeared to originate on the right side of the head and shift leftward. These effects were diminished when the first four lights were all presented on one side of the CRT and the last four lights were all presented on the other side of the CRT. This multimodal phenomenon occurs although the light was perceived external to the head while the sounds presented over headphones were perceived within the head.

Acoustic Stimulation↗

PubMed2005

Depletion of Bmp2, Bmp4, Bmp7 and Spemann organizer signals induces massive brain formation in Xenopus embryos.

To address the patterning function of the Bmp2, Bmp4 and Bmp7 growth factors, we designed antisense morpholino oligomers (MO) that block their activity in Xenopus laevis. Bmp4 knockdown was sufficient to rescue the ventralizing effects caused by loss of Chordin activity. Double Bmp4 and Bmp7 knockdown inhibited tail development. Triple Bmp2/Bmp4/Bmp7 depletion further compromised trunk development but did not eliminate dorsoventral patterning. Unexpectedly, we found that blocking Spemann organizer formation by UV treatment or beta-Catenin depletion caused BMP inhibition to have much more potent effects, abolishing all ventral development and resulting in embryos having radial central nervous system (CNS) structures. Surprisingly, dorsal signaling molecules such as Chordin, Noggin, Xnr6 and Cerberus were not re-expressed in these embryos. We conclude that BMP inhibition is sufficient for neural induction in vivo, and that in the absence of ventral BMPs, Spemann organizer signals are not required for brain formation.

Animals↗