Should spikes be treated with equal weightings in the generation of spectro-temporal receptive fields?

Knowledge on the trigger features of central auditory neurons is important in the understanding of speech processing. Spectro-temporal receptive fields (STRFs) obtained using random stimuli and spike-triggered averaging allow visualization of trigger features which often appear blurry in the time-versus-frequency plot. For a clearer visualization we have previously developed a dejittering algorithm to sharpen trigger features in the STRF of FM-sensitive cells. Here we extended this algorithm to segregate spikes, based on their dejitter values, into two groups: normal and outlying, and to construct their STRF separately. We found that while the STRF of the normal jitter group resembled full trigger feature in the original STRF, those of the outlying jitter group resembled a different or partial trigger feature. This algorithm allowed the extraction of other weaker trigger features. Due to the presence of different trigger features in a given cell, we proposed that in the generation of STRF, the evoked spikes should not be treated indiscriminately with equal weightings.

Effect of acupuncture at nei-kuan on left ventricular function in patients with coronary artery disease.

Effect of acupuncture at Nei-Kuan (EH-6) on left ventricular ejection fraction (LVEF) was examined in 22 patients with angiographically proved coronary artery disease (CAD) and 22 normal subjects. Serial equilibrium radionuclide angiography was done to measure LVEF at 4 different times (at baseline, at 1 to 15 minutes, and 16 to 30 minutes during acupuncture, and immediately after acupuncture). One week later, each patient had an identical imaging protocol with acupuncture performed at a dummy point. Our results showed that in normal subjects, the mean values of LVEF did not change significantly during or after acupuncture. In contrast, in patients with CAD, the mean values of LVEF in the initial 15 minutes of acupuncture significantly increased from baseline (42.5 +/- 15.6% vs. 40.6 +/- 15.4%, p < 0.05). The increase persisted through the next 15 minutes of acupuncture and 15 minutes after acupuncture, but became insignificant at one week. Thus, acupuncture at Nei-Kuan can temporarily improve LV function in patients with CAD.

Transient frequency and intensity sensitivities of central auditory neurons determined with sweep tone.

To determine the transient frequency and intensity sensitivities of central auditory neurons, we implemented an exponential sweep tone stimulus (2 sec in period, mean sweep rate 3.3 octave/sec), intensity of which varied systematically across trials. Response of single units to the stimulus was studied at the inferior colliculus (IC) of urethane-anesthetized rats. Most IC units responded to the sweep tone by one or more transient increases in discharge rate. The area of increased discharge, or response area (RA), was delineated on the frequency-intensity plane. The tip of RA gives the best frequency (BF) and minimum threshold (MT) of the cell. We also compared the BF and MT concurrently obtained with another method, viz., the conventional 'audio-visual' method of subjective judgment. Results showed that for the same population of cells (n=130), correlation between the two methods is better for BF (r=0.91) than for MT (r=0.78). Such discrepancy was discussed in relation to the response characteristics of these central auditory neurons.