Navigating with fingers and feet: analysis of human (Homo sapiens) and rat (Rattus norvegicus) movement organization during nonvisual spatial tasks

Application of scaling to mouse spontaneous movement: Path curvature varies with speed and linear distance features isochrony

To conserve sequential behavior in relation to the topographic challenges of space, it is proposed that humans and nonhuman animals can organize behavior using different scaling principles. To deal with increases in linear distance, isochrony suggest that there is a corresponding increase in speed, whereas to deal with changes in curvature, speed is adjusted according to a power function. The present study investigates whether these principles provide a framework for describing the organization of mouse behavior in a variety of standard experimental tasks. The structure of movement was examined in ambulation during open field exploration; manipulation in a string-pulling task, in which a string is advanced hand over hand to retrieve food; and rung-walking, in which the limbs successively step from rung to rung on a horizontal ladder. Both principles were found to be conserved in the organization of mouse behavior across scales of movement. These principles provide novel measures of the temporal and geometric features of movement in the mouse and insights into how the temporal and geometric features of movement are conserved within different species.

Sexually dimorphic organization of open field behavior following moderate prenatal alcohol exposure

BACKGROUND

Prenatal alcohol exposure (PAE) can produce deficits in a wide range of cognitive functions but is especially detrimental to behaviors requiring accurate spatial information processing. In open field environments, spatial behavior is organized such that animals establish "home bases" marked by long stops focused around one location. Progressions away from the home base are circuitous and slow, while progressions directed toward the home base are non-circuitous and fast. The impact of PAE on the organization of open field behavior has not been experimentally investigated.

METHODS

In the present study, adult female and male rats with moderate PAE or saccharin exposure locomoted a circular high walled open field for 30 minutes under lighted conditions.

RESULTS

The findings indicate that PAE and sex influence the organization of open field behavior. Consistent with previous literature, PAE rats exhibited greater locomotion in the open field. Novel findings from the current study indicate that PAE and sex also impact open field measures specific to spatial orientation. While all rats established a home base on the periphery of the open field, PAE rats, particularly males, exhibited significantly less clustered home base stopping with smaller changes in heading between stops. PAE also impaired progression measures specific to distance estimation, while sex alone impacted progression measures specific to direction estimation.

CONCLUSIONS

These findings support the conclusion that adult male rats have an increased susceptibility to the effects of PAE on the organization of open field behavior.

A speed-accurate self-sustaining head direction cell path integration model without recurrent excitation

The head direction (HD) system signals HD in an allocentric frame of reference. The system is able to update firing based on internally derived information about self-motion, a process known as path integration. Of particular interest is how path integration might maintain concordance between true HD and internally represented HD. Here we present a self-sustaining two-layer model, capable of self-organizing, which produces extremely accurate path integration. The implications of this work for future investigations of HD system path integration are discussed.

Otolithic information is required for homing in the mouse

Navigation and the underlying brain signals are influenced by various allothetic and idiothetic cues, depending on environmental conditions and task demands. Visual landmarks typically control navigation in familiar environments but, in the absence of landmarks, self-movement cues are able to guide navigation relatively accurately. These self-movement cues include signals from the vestibular system, and may originate in the semicircular canals or otolith organs. Here, we tested the otolithic contribution to navigation on a food-hoarding task in darkness and in light. The dark test prevented the use of visual cues and thus favored the use of self-movement information, whereas the light test allowed the use of both visual and non-visual cues. In darkness, tilted mice made shorter-duration stops during the outward journey, and made more circuitous homeward journeys than control mice; heading error, trip duration, and peak error were greater for tilted mice than for controls. In light, tilted mice also showed more circuitous homeward trips, but appeared to correct for errors during the journey; heading error, trip duration, and peak error were similar between groups. These results suggest that signals from the otolith organs are necessary for accurate homing performance in mice, with the greatest contribution in non-visual environments.

Walking in circles: navigation deficits from Parkinson's disease but not from cerebellar ataxia

Little is known on the role of neuronal structures for spatial navigation. Our goal was to examine how Parkinson's disease (PD) and cerebellar ataxia, as human lesion models of the basal ganglia and cerebellum, affect spatial navigation round a circular walking path, blindfolded. Twelve subjects with idiopathic PD (ON and OFF medication), eight subjects with cerebellar ataxia and a control group of 20 age-matched healthy subjects participated. All groups performed well when walking around the circle with eyes open. In the eyes-closed condition, control subjects overshot the outlined trajectory but returned to their initial position, thus walking a further distance with eyes closed than with eyes open. When OFF medication, PD subjects navigated a larger radius than controls with eyes closed. When ON levodopa, PD subjects walked a similar distance as controls but with even larger errors in endpoint. Surprisingly, cerebellar patients navigated the circular walking task in the eyes closed condition with even more accuracy (i.e. following the outlined circle) than control and PD subjects. We conclude that blindfolded navigation around a previously seen circle requires intact basal ganglia, but not cerebellar input.