Effects of cortisol on hippocampal subfields volumes and memory performance in healthy control subjects and patients with major depressive disorder.

Overactivity of the hypothalamic-pituitary-adrenal (HPA) axis in major depressive disorder (MDD) is among the most consistently replicated biological findings in psychiatry. Magnetic resonance imaging (MRI) studies have consistently demonstrated that hippocampal (HC) volume is decreased in patients with MDD. The improved spatial resolution of high field strength MRI has recently enabled measurements of HC subfield volumes in vivo. The main goal of the present study was to examine the relationship between cortisol concentrations over a day and HC subfield volumes in patients with MDD compared to healthy controls and to investigate whether diurnal cortisol measures are related to memory performance. Fourteen MDD patients with moderate or severe episodes were recruited, together with 14 healthy controls. Imaging was performed using a 4.7T whole-body imaging system. HC subfields and subregions were segmented manually using previously defined protocol. Memory performance was assessed using the Wechsler Memory Scale IV. The salivary cortisol levels were measured over the course of one day. We found that cortisol awakening response to 8h (CAR-8h) was higher in MDD patients compared to controls and that this increase in CAR-8h in MDD patients correlated negatively with left total Cornu Ammonis (CA)1-3 and left HC head volume. In healthy controls mean cortisol levels were negatively associated with right total CA1-3, right HC head, and right total HC volume. In addition, in healthy controls higher CAR-8h was related to worse performance on the immediate content memory. These results provide the first in vivo evidence of the negative associations between cortisol level, CA1-3 HC subfield volume and memory performance in patients with MDD and healthy controls.

Drug treatment and familiar music aids an attention shift from vision to somatosensation in Parkinson's disease on the reach-to-eat task.

Sensory control of the natural skilled movement of reaching for a food target to eat (reach-to-eat) is closely coupled to the successive phases of the movement. Control subjects visually fixate the target from hand movement onset to the point that the digits contact the food, at which point they look away. This relationship between sensory attention and limb movement suggests that whereas limb advance is under visual control, grasping, limb withdrawal, and releasing the food to the mouth is guided by somatosensation. The pattern of sensory control is altered in Parkinson's disease (PD). PD subjects may visually fixate the target for longer durations prior to movement initiation, during the grasp, and during the initial portion of hand withdrawal suggesting that vision compensates for a somatosensory impairment. Because both medication and listening to favorite musical pieces have been reported to normalize some movements in subjects with PD, the present study compared the effect of medication and listening to preferred musical pieces on sensory attention shifts from vision to somatosensation during the reach-to-eat movement. Biometric measures of eye movement and the movement of the reaching limb were collected from PD subjects and aged-matched control subjects in four conditions in their own homes: off medication, off medication with music, on medication, and on medication with music. Unmedicated PD subjects were slower to visually disengage the target after grasping it. Their disengage latency was shortened by both music and medication. Medication and music did not improve other aspects of reaching, including reaching duration and the ratings of the movement elements of limb advance, grasping, and limb withdrawal. The results are discussed in relation to the idea that one way in which medication and music may aid movement in PD by normalizing somatosensory control of forelimb movement thus reducing compensatory visual monitoring.

The functional origins of speech-related hand gestures.

Many theories of language posit its recent evolution, perhaps contemporaneous with the evolution of Homo sapiens. The embodied language theory, however, in proposing that language includes gestures, provides an avenue for tracing language origins to phylogenetically earlier ancestral species. Here, evidence is presented that the structure of functional hand movements (e.g., reaching for food, climbing a ladder, or crawling), in rats and humans is similar. The structure of these functional hand movements is then compared to speech-related hand gestures in humans. The sequence of language-related gestures are also found to be characteristic of functional hand movements. It is suggested that these findings show that the arm and hand gestures that accompany human speech are derived from the same neural substrates that produce functional movements. Additionally, evidence is reviewed that supports the idea that speech-related gestures resemble the movements elicited by long-train stimulation of the primate motor cortex. Together, this evidence suggests that speech-related hand gestures have their evolutionary origins in functional hand movements of ancestral non-primate and primate species and may be constrained by the neural substrate for those movements. These findings are further discussed in relation to the idea that speech-related gestures reflect forelimb motor cortex contributions to embodied language.

Hippocampal damage produces retrograde but not anterograde amnesia for a cued location in a spontaneous exploratory task in rats.

Performance in several memory tasks is known to be unaffected by hippocampal damage sustained before learning, but is severely disrupted if the same damage occurs after learning. Memories for preferred locations, or home bases, in exploratory tasks can be formed by rats with hippocampal damage, but it is unknown if the memory for a home base survives hippocampal damage. To examine this question, for 30 min each day for five consecutive days, rats explored a circular open field containing one local cue. By Day 5 the rats preferentially went directly to that location, spent the majority of their time at that location, made rapid direct trips to that location when returning from an excursion and so demonstrated that the location was a home base. Memory for the cued location was examined after a 24 h or 14-day interval with the cue removed. In Experiments 1 and 2, control rats and rats with prior N-methyl-D-aspartic acid hippocampal lesions demonstrated memory of the home base location by making direct trips to that location. In Experiment 3, rats that had first explored the open field and cue and then received hippocampal lesions showed no memory for the cued location. The absence of anterograde impairment vs. the presence of retrograde impairment for memory of a spatial home base confirms a role for the hippocampus in the retention of spatial memory acquired during exploration.

Hand shaping in the rat: conserved release and collection vs. flexible manipulation in overground walking, ladder rung walking, cylinder exploration, and skilled reaching.

Hand shaping in terrestrial mammals is adapted to many functions including walking, climbing, exploration, and skilled manipulation. Nevertheless, hand shaping is not well described in the rat (Rattus norvegicus) although the species is used to study the evolution of movement, the neural control of movement, and to model impairments that can result from brain injury. In the present study, rat hand movements were examined in standardized tests of overground walking, horizontal or inclined ladder rung walking, exploring a vertical wall of a cylinder, and skilled reaching for food. Behavior was filmed with high-speed (250-1000 f/s) video camera from which frame-by-frame behavioral and kinematic analyses (Peak Motus) were made. There were three hand actions common to all tasks. In release, the hand pushed off or was lifted from a substrate; in collection, the digits were closed and flexed though the midpoint of limb transport; and, in manipulation, the hand and digits were shaped to contact or grasp a target. The movements of release and collection, although variable in character, speed and duration, were very similar in the different tests. The movement of manipulation featured greater specialized digit use and varied sensory control (olfaction, vibrissae, and tactile senses) in different tasks. Conserved release and collection vs. the variability of manipulation is discussed in relation to the evolution, neural control, and neural commitment underlying hand movements.