Hypothalamic and zona incerta neurons in sheep, initially only responding to the sight of food, also respond to the sight of water after intracerebroventricular injection of hypertonic saline or angiotensin II

Extracellular single-unit recordings were made from neurons in the lateral hypothalamus (LH) or zona incerta (ZI) of conscious sheep. A small population of neurons (12/83) were found which responded with increased firing rate when the animal looked at food but did not respond when the sheep looked at water. The effects of rapidly inducing intense thirst by the intracerebroventricular (i.c.v.) injection of hypertonic (0.85 M) saline or 200 ng of angiotensin II, or a mixture of the two dipsogenic stimuli, on the response of neurons initially responding only to the sight of food were investigated. Following i.c.v. injection of the dipsogenic stimuli the neurons began to respond strongly to the sight of water. The results demonstrated that changing the animal's motivational state alters the response of some neurons in the LH and ZI and suggests that the neuronal response is influenced by the animal's dominant need at the time of testing.     

Preattentive discrimination of across-category and within-category change in consonant-vowel syllable

Event-related potentials to infrequently presented spoken deviant syllables /pi/ and /po/ among repetitive standard [see text] syllables were recorded in Thai study participants who ignored these stimuli while reading books of their choices. The vowel across-category and within-category changes elicited a change-specific mismatch negativity response. The across-category and within-category change discrimination of vowels in consonant-vowel syllable was also assessed using the low-resolution electromagnetic tomography. The results of low-resolution electromagnetic tomography mismatch negativity generator analysis suggest that the within-category change perception of vowels is analyzed as the change in physical features of the stimuli, thus predominantly activating the right temporal cortex. In contrast, the left temporal cortex is predominantly activated in the across-category change perception of vowels, emphasizing the role of the left hemisphere in speech processing already at a preattentive processing level also in consonant-vowel syllables. The results support the hypothesis that a part of the superior temporal gyrus contains neurons specialized for speech perception.