Automated apparatus for quantitation of social approach behaviors in mice.

Mouse models of social dysfunction, designed to investigate the complex genetics of social behaviors, require an objective methodology for scoring social interactions relevant to human disease symptoms. Here we describe an automated, three chambered apparatus designed to monitor social interaction in the mouse. Time spent in each chamber and the number of entries are scored automatically by a system detecting photocell beam breaks. When tested with the automated equipment, juvenile male C57BL/6J mice spent more time in a chamber containing a stranger mouse than in an empty chamber (sociability), similar to results obtained by the observer scored method. In addition, automated scoring detected a preference to spend more time with an unfamiliar stranger than a more familiar conspecific (preference for social novelty), similar to results obtained by the observer scored method. Sniffing directed at the wire cage containing the stranger mouse correlated significantly with time spent in that chamber, indicating that duration in a chamber represents true social approach behavior. Number of entries between chambers did not correlate with duration of time spent in the chambers; entries instead proved a useful control measure of general activity. The most significant social approach behavior took place in the first five minutes of both the sociability and preference for social novelty tests. Application of these methods to C57BL/6J, DBA/2J and FVB/NJ adult males revealed that all three strains displayed tendencies for sociability and preference for social novelty. To evaluate the importance of the strain of the stranger mouse on sociability and preference for social novelty, C57BL/6J subject mice were tested either with A/J strangers or with C57BL/6J strangers. Sociability and preference for social novelty were similar with both stranger strains. The automated equipment provides an accurate and objective approach to measuring social tendencies in mice. Its use may allow higher-throughput scoring of mouse social behaviors in mouse models of social dysfunction.

Alterations in cerebral blood flow produced by hypotension: a comparison of methods.

Alterations in cerebral blood flow produced by controlled episodes of hypotension were studied in 12 juvenile monkeys using a thermocouple techique. The qualitative changes observed agreed closely with those obtained from an earlier study employing [14C]antipyrine autoradiographic methods. The present study extends the validity of the earlier antipyrine investigations by means of the continuous recording. The advantages and disadvantages of the thermocouple technique are examined.

Changes in cortical impedance and EEG activity induced by profound hypotension.

Fourteen late juvenile monkeys were subjected to a single 30-min episodes of markedhypotension using an infusion of trimethaphan. Afterward, blood pressure was rapidly restored to and maintained at preinsult levels with an intravenous drip of phenylephrine (.02 mg/ml). The respiratory gas tensions and pH of the arterial blood weremaintained within normal limits at all times. During the 30-min episodes, the cortical electrical impedence increased by a mean of 27% while the EEG frequencies and amplitudes decreased by 47 and 30%, respectively. The impedance and EEG activity generally altered at the same time but inversely to one another, although, on restoration of blood pressure, the impedance recovered within minutes while the EEG activity returned to normal only after 1 h. The impedance values and EEG activity of those animals that eventually died began to diverge significantly from the values of theanimals that were to survive at about 2.5 h after restoration of blood pressure.

Activation of the primary visual cortex by Braille reading in blind subjects.

Primary visual cortex receives visual input from the eyes through the lateral geniculate nuclei, but is not known to receive input from other sensory modalities. Its level of activity, both at rest and during auditory or tactile tasks, is higher in blind subjects than in normal controls, suggesting that it can subserve nonvisual functions; however, a direct effect of non-visual tasks on activation has not been demonstrated. To determine whether the visual cortex receives input from the somatosensory system we used positron emission tomography (PET) to measure activation during tactile discrimination tasks in normal subjects and in Braille readers blinded in early life. Blind subjects showed activation of primary and secondary visual cortical areas during tactile tasks, whereas normal controls showed deactivation. A simple tactile stimulus that did not require discrimination produced no activation of visual areas in either group. Thus in blind subjects, cortical areas normally reserved for vision may be activated by other sensory modalities.