Biomedical subjects

H M Mai

Publications and source records attributed to H M Mai.

2 recordsLinked to original sources

PubMed2007

Spatio-temporal analysis of feature-based attention.

The cortical mechanisms of feature-selective attention to color and motion cues were studied in humans using combined electrophysiological, magnetoencephalographic, and hemodynamic (functional magnetic resonance imaging) measures of brain activity. Subjects viewed a display of random dots that periodically either changed color or moved coherently. When attention was directed to the color change it elicited enhanced neural activity in visual area V4v, previously shown to be specialized for processing color information. In contrast, when dot movement was attended it produced enhanced activity in the motion-specialized area human MT. Parallel recordings of event-related electrophysiological and magnetoencephalographic responses indicated that the attention-related facilitation of neural activity in these specialized cortical areas occurred rapidly, beginning as early as 90-120 ms after stimulus onset. We conclude that selection of an entire feature dimension (motion or color) boosts neural activity in its specialized cortical module much more rapidly than does selection of one feature value from another (e.g., one color from another), as reported in previous electrophysiological studies. By combining methods with high spatial and temporal resolution it is possible to analyze the precise time course of feature-selective processing in specialized cortical areas.

Adult↗

PubMed2002

Detection of oestrus in Bunaji cows under field conditions.

The objective of this study was to determine the efficacy of some aids for detecting oestrus in 72 Bunaji cows synchronized using two injections of prostaglandin F2 alpha (PGF2 alpha) 13 days apart. Blood samples to determine the accuracy of the aids and ovarian activity by radioimmunoassay technique were collected daily from the day of the second PGF2 alpha injection until oestrus or for 168 hours for 'non-responders'. The aids for detecting oestrus, tail painting, KaMar detectors and a chin-ball mating device (CMD) were applied at the time of the second injection. The oestrus response rate was 73.6% and 61.1%, from the serum progesterone concentration and visual observation, respectively. Based on the total number of oestrus events observed, unaided visual observation, tail painting, KaMar and CMD detected 52.2%, 82.6%, 82.6% and 76.8%, respectively. Visual observation of standing oestrus alone failed to detect 47.8% of the occurrence of oestrus as shown by the concentration of progesterone in the serum and 30.4%, 30.4% and 24.6%, respectively, of the oestrus periods recorded by tail painting, KaMar and CMD. Twenty-eight cows showed abnormalities in progesterone concentration. These investigations showed that oestrus may be detected by using the aids in cows that have been regarded as 'anoestrous' by visual observation of standing heat.

Animals↗