Melville J Wohlgemuth

• B.S., M.Phil., Ph.D.
• Professor (Assistant) at University of Arizona

Rapid categorization of vocalizations enables adaptive behavior across species. While categorical perception is thought to arise in the neocortex, humans and other animals could benefit from functional organization of ethologically-relevant sounds at earlier stages in the auditory hierarchy. Here, we developed two-photon calcium imaging in the awak...

James Simmons’s early research on sonar ranging in echolocating bats generated two groundbreaking discoveries: (1) Bats compute object distance from the time delay between sonar calls and echoes, and they discriminate echo-delay differences in the microsecond range [Simmons, https://psycnet.apa.org/doi/10.1121/1.1913559 (1973)] and (2) A population...

Echolocating bats are among the only mammals capable of powered flight, and they rely on active sensing to find food and steer around obstacles in 3D environments. These natural behaviors depend on neural circuits that support 3D auditory localization, audio-motor integration, navigation, and flight control, which are modulated by spatial attention...

Animals utilize a variety of active sensing mechanisms to perceive the world around them. Echolocating bats are an excellent model for the study of active auditory localization. The big brown bat (Eptesicus fuscus), for instance, employs active head roll movements during sonar prey tracking. The function of head rolls in sound source localization i...

Landmark-guided navigation is a common behavioral strategy for way-finding, yet prior studies have not examined how animals collect sensory information to discriminate landmark features. We investigated this question in animals that rely on active sensing to guide navigation. Four echolocating bats (Eptesicus fuscus) were trained to use an acoustic...

A large body of laboratory research has investigated the process by which environmental cues are acquired and used for spatial navigation in rodents; however, the key to differentiating between species specializations and general principles lies in comparative research. Rodent research has focused on a class of neurons in the hippocampus implicated...

Echolocating bats dynamically adapt the features of their sonar calls as they approach obstacles and track targets. As insectivorous bats forage, they increase sonar call rate with decreasing prey distance, and often embedded in bat insect approach sequences are clusters of sonar sounds, termed sonar sound groups (SSGs). The bat's production of SSG...

Echolocating bats often forage in the presence of both conspecific and heterospecific individuals who have the potential to produce acoustic interference. Recent studies have shown that at least one bat species, the Brazilian free-tailed bat (Tadarida brasiliensis), produces specialized social signals that disrupt the sonar of conspecific competito...

Essential to spatial orientation in the natural environment is a dynamic representation of direction and distance to objects. Despite the importance of 3D spatial localization to parse objects in the environment and to guide movement, most neurophysiological investigations of sensory mapping have been limited to studies of restrained subjects, test...

(A) Comparison of the variance of SSG and non-SSG distance tuning distributions for each cell in Figure 5D. The SSG and non-SSG distance tuning distributions were compared using the non-parametric Brown-Forsythe Test at the level α of 0.05. Cells in red show a significant sharpening in the distance tuning distribution when the bat emitted SSGs as c...

Sensory-guided behaviors require the transformation of sensory information into task-specific motor commands. Prior research on sensorimotor integration has emphasized visuomotor processes in the context of simplified orienting movements in controlled laboratory tasks rather than an animal’s more complete, natural behavioral repertoire. Here, we co...

No PDF available ABSTRACT Our natural world is three-dimensional. A fundamental requirement of spatial orientating behaviors in the natural environment is the representation of 3D sensory space. Despite the importance of 3D sensory coding of a natural scene to guide movement, most neurophysiological investigations of this problem have been limited...

Spatial navigation by echolocation in bats is an active and adaptive system: Its success depends upon tight coupling between motor commands for sonar signal production and neural processing that supports spatial perception and attention to objects in the 3D environment. The midbrain superior colliculus (SC) has been implicated in sensorimotor trans...

Under natural conditions, animals encounter a barrage of sensory information from which they must select and interpret biologically relevant signals. Active sensing can facilitate this process by engaging motor systems in the sampling of sensory information. The echolocating bat serves as an excellent model to investigate the coupling between actio...

Change in inter-pinna separation on a per-trial basis. Three individual trials demonstrating both the gradual change in inter-pinna separation with changing target distance, as well as abrupt, small changes on a shorter timescale. Data for this figure can be found at http://dx.doi.org/10.7281/T1W66HPZ. (EPS)

Tracking a moving target from a stationary position. In this three-part video, the bat is shown tracking a moving insect from a stationary position on a platform. The first segment is one trial of the bat tracking an insect from a view 3 meters in front of the bat. The second segment is a zoomed version of one trial of a bat tracking an insect. In...

Measuring movements of the head and ears. This video has four different panels describing the technique for recording the 3-D positions of the head and ears in time synchrony with recordings of sonar vocalizations. The top-left panel displays the inter-pinna distance; the top-right panel displays the 3-D positions of the head and two ear markers; t...

Degree offset of pinna during head waggles. Plotted is the maximum angular displacement of the tips of the pinnae during head waggles as a function of target distance. In black is the average maximum displacement, and the red shaded region indicates +/- 1 standard deviation of the average. Inset, distribution of all angles subtended by the two ears...

Raising and lowering the pinnae to change inter-pinna separation. Top, inter-pinna separation as measured by the distance between the tips of the pinna in three dimensions. Bottom, difference in elevation (z-axis) of tips of pinna and marker on the head. As inter-pinna distance decreases, there is a concomitant increase in the z-distance between th...

Decoupling local peaks in inter-pinna separation with vocal behaviors. Shown are nine different trials of inter-pinna separation during the tracking of the one-target simple motion condition. Highlighted are three different instances of the decoupling pinna movements from sonar vocalizations. Blue arrows indicate times when local peaks in inter-pin...

Demonstration of the bats? head waggle. This is a two-part movie showing the waggling of the head performed by the bat while tracking an insect. The first segment is shown at actual speed, and the bat?s vocalizations are audible through a bat detector. The second segment of the video was collected with high-speed recording and slowed down by a fact...

Significant differences in sonar pulse interval across target motions. (A) D-prime (d?) calculation between one-target simple and one-target complex pulse intervals as a function of target distance. Red shaded regions indicate significant differences as determined by a permutation test, indicating time points of significant differences. (B) d? calc...

Significant differences in sonar pulse duration across target motions. (A) d? calculation between one-target simple and one-target complex pulse durations as a function of target distance. Red shaded regions indicate significant differences as determined by a permutation test, indicating time points of significant differences. (B) d? calculation be...

Sonar sound group production. (A) Example of sonar sound group. Top, oscillogram of series of vocalizations produced while tracking a moving target. Bottom, highlight of three sonar sound groups: two doublets (two calls) and one triplet (three calls), demonstrating the shorter and regular pulse interval of the sonar group, surrounded by calls of lo...

Time lag from change in target motion and change in pinna separation. (A) Top, one-target complex motion; bottom, inter-pinna separation for one trial of one-target complex motion. (B) Sliding cross correlations for ten example trials of inter-pinna separation during one-target complex tracking. Note that target motion was inverted in panel A for t...

Change in sonar acoustics with target distance. Change in the end frequency of sonar vocalizations with decreasing target distance. Plotted is the mean +/- s.e.m., with end frequency significantly correlated with target distance (Pearson?s correlation, r = 0.34, p < 0.0001). Data for this figure can be found at http://dx.doi.org/10.7281/T1W66HPZ. (...

Echolocating bats exhibit accurate three-dimensional (3D) auditory localization to avoid obstacles and intercept prey. The bat achieves high spatial resolution through a biological sonar system. Key features of the bat's sonar system are (1) high frequency, directional echolocation signals; (2) high frequency hearing; (3) mobile ears; and (4) measu...

Significance Nervous systems have evolved to enable processing of complex stimuli that animals encounter in their natural environments, and yet, neurophysiological research has largely investigated responses to simple artificial stimuli. In an attempt to bridge this gap, we characterized response selectivity to natural stimuli in the midbrain super...

Echolocating bats are equipped with a biological sonar system that permits spatial navigation and target tracking in complete darkness. By actively controlling the directional aim, timing, frequency content, and duration of echolocation signals to “illuminate” the environment, the bat directly influences the acoustic input available to its sonar im...

To successfully negotiate a cluttered environment, an echolocating bat must control the timing of motor behaviors in response to dynamic sensory information. Here we detail the big brown bat's adaptive temporal control over sonar call production for tracking prey, moving predictably or unpredictably, under different experimental conditions. We stud...

To accurately select and orient to a target, noisy, and multimodal sensory information about the target's location must be integrated into a coordinated set of orienting movements. At the hub of sensorimotor integration for species-specific orientation is the superior colliculus (SC), a midbrain structure receiving multimodal sensory inputs and pro...

Spatially guided behaviors in echolocating bats depend upon the dynamic interplay between auditory information processing and adaptive motor control. The bat produces ultrasonic signals and uses information contained in the returning echoes to determine the direction and distance of objects in space. With this acoustic information, the echolocating...

The control of sequenced behaviors, including human speech, requires that the brain coordinate the production of discrete motor elements with their concatenation into complex patterns. In birdsong, another sequential vocal behavior, the acoustic structure (phonology) of individual song elements, or "syllables," must be coordinated with the sequenci...

Birdsong is a learned behavior remarkable for its high degree of stereotypy. Nevertheless, adult birds display substantial rendition-by-rendition variation in the structure of individual song elements or "syllables." Previous work suggests that some of this variation is actively generated by the avian basal ganglia circuitry for purposes of motor e...

Thalamic nuclei are thought to funnel sensory information to the brain's primary cortical areas, which in turn transmit signals afresh to higher cortical areas. Here we describe a direct projection in the macaque monkey from the lateral geniculate nucleus (LGN) to the motion-selective middle temporal area (MTor V5), a cortical area not previously c...

leakage into the white matter. In addition, MT in macaques is com- pletely buried in the superior temporal sulcus (STS), and it lacks well- defined cytoarchitectonic boundaries. These factors make it challenging to place tracer injections accurately into MT without spillover into surrounding cortical areas. Thus a definitive verdict about the exist...