MDMA and memory, addiction, and depression: dose-effect analysis.

Rationale: ±3,4-Methylenedioxymethamphetamine (MDMA) is a recreational drug that shows substantial promise as a psychotherapeutic agent. Still, there is some concern regarding its behavioral toxicity, and its dose-effect relationship is poorly understood. We previously explored the role of dose in the cognitive effects of MDMA in a systematic review of existing literature and found no evidence in animals that MDMA impairs memory at low doses (< 3 mg/kg) but mixed results at high doses (≥ 3 mg/kg).

Spectral cues and temporal integration during cylinder echo discrimination by bottlenose dolphins (Tursiops truncatus).

Three bottlenose dolphins (Tursiops truncatus) participated in simulated cylinder wall thickness discrimination tasks utilizing electronic "phantom" echoes. The first experiment resulted in psychometric functions (percent correct vs wall thickness difference) similar to those produced by a dolphin performing the task with physical cylinders. In the second experiment, a wide range of cylinder echoes was simulated, with the time separation between echo highlights covering a range from <30 to >300 μs.

Quantifying the Acoustic Startle Response in Mice Using Standard Digital Video.

The startle response is an unconditional reflex, characterized by the rapid contraction of facial and skeletal muscles, to a sudden and intense startling stimulus. It is an especially useful tool in translational research for its consistency across species, simple neural circuitry, and sensitivity to a variety of experimental manipulations. The rodent acoustic startle response is commonly used to study fundamental properties of the central nervous system, including habituation, sensitization, classical conditioning, fear and anxiety, sensorimotor gating, and drug effects.

Higher neuron densities in the cerebral cortex and larger cerebellums may limit dive times of delphinids compared to deep-diving toothed whales.

Since the work of Tower in the 1950s, we have come to expect lower neuron density in the cerebral cortex of larger brains. We studied dolphin brains varying from 783 to 6215g. As expected, average neuron density in four areas of cortex decreased from the smallest to the largest brain.

Composite critical ratio functions for odontocete cetaceans.

Critical ratios (CRs) are useful for estimating detection thresholds of tonal signals when the spectral density of noise is known. In cetaceans, CRs have only been measured for a few animals representing four odontocete species. These data are sparse, particularly for lower frequencies where anthropogenic noise is concentrated.

Comparison of Dolphins' Body and Brain Measurements with Four Other Groups of Cetaceans Reveals Great Diversity.

We compared mature dolphins with 4 other groupings of mature cetaceans. With a large data set, we found great brain diversity among 5 different taxonomic groupings. The dolphins in our data set ranged in body mass from about 40 to 6,750 kg and in brain mass from 0.

On doing two things at once: dolphin brain and nose coordinate sonar clicks, buzzes and emotional squeals with social sounds during fish capture.

Dolphins fishing alone in open waters may whistle without interrupting their sonar clicks as they find and eat or reject fish. Our study is the first to match sound and video from the dolphin with sound and video from near the fish. During search and capture of fish, free-swimming dolphins carried cameras to record video and sound.