Anne-Kathrin Warzecha

• Dr. rer nat
• Bielefeld University

Synergies of Art and Science Lecture via Zoom, 17.06. 6-8 PM CET While science conveys information via rational arguments, works of art change our perception of reality in much more diverse and maybe more substantial ways Art can thus play an essential role in rising the public’s awareness about the reality and consequences of climate change and...

Interdisciplinary conversation between UN-diplomat Dr. Martin Frick, Deputy to the Special Envoy for the Food Systems Summit 2021, and soil- and food systems scientist Dr. Benjamin Bodirsky (Potsdam Institute for Climate Impact Research) about foodsecurity and climatechange. Lecture starts at 6 PM CET on Jan. 21, 2021.

One point often raised during the discussions was the interdependence of function and structure. Several examples clearly showed that natural organisms have developed a lot of specialized organs or strategies (facette eye of the fly, interpretation of sensory inputs within the behavioral context), which are useful for the organism in the natural en...

Arthropods live in almost any conceivable habitat. Accordingly, structural and functional specialisations have been described in many species which allow them to behave in an adaptive way with the limited computational resources of their small brains. These adaptations range from the special design of the eyes, the spectral sensitivities of their p...

Nervous systems encode information about dynamically changing sensory input by changes in neuronal activity. Neuronal activity changes, however, also arise from noise sources within and outside the nervous system or from changes of the animal's behavioral state. The resulting variability of neuronal responses in representing sensory stimuli limits...

Behavioral responses of an animal vary even when they are elicited by the same stimulus. This variability is due to stochastic processes within the nervous system and to the changing internal states of the animal. To what extent does the variability of neuronal responses account for the overall variability at the behavioral level? To address this q...

So far, it remains largely unresolved to what extent neuronal noise affects behavioral responses. Here, we investigate, where in the human visual motion pathway noise originates that limits the performance of the entire system. In particular, we ask whether perception and eye movements are limited by a common noise source, or whether processing sta...

The strength of stimulus-induced responses at the neuronal and the behavioural level often depends on the internal state of an animal. Within pathways processing sensory information and eventually controlling behavioural responses, such gain changes can originate at several sites. Using motion-sensitive lobula plate tangential cells (LPTCs) of blow...

Behavioural responses of an animal are variable even when the animal experiences the same sensory input several times. This variability can arise from stochastic processes inherent to the nervous system. Also, the internal state of an animal may influence a particular behavioural response. In the present study, we analyse the variability of visuall...

We investigate the impact of monitor frame rate on the human ocular following response (OFR) and find that the response latency considerably depends on the frame rate in the range of 80-160 Hz, which is far above the flicker fusion limit. From the lowest to the highest frame rate the latency declines by roughly 10 ms. Moreover, the relationship bet...

Response variability is a fundamental issue in neural coding because it limits all information processing. The reliability of neuronal coding is quantified by various approaches in different studies. In most cases it is largely unclear to what extent the conclusions depend on the applied reliability measure, making a comparison across studies almos...

Neurons embedded in networks are thought to receive synaptic inputs that do not drive them on their own, but modulate the responsiveness to driving input. Although studies on brain slices have led to detailed knowledge of how nondriving input affects dendritic integration, its origin and functional implications remain unclear. We tackle this issue...

Variable behavioral responses to identical visual stimuli can, in part, be traced back to variable neuronal signals that provide unreliable information about the outside world. This unreliability in encoding of visual information is caused by several noise sources such as photon noise, synaptic noise, or the stochastic nature of ion channels. Neuro...

To understand the functioning of nervous systems and, in particular, how they control behaviour we must bridge many levels of complexity from molecules, cells and synapses to perception behaviour. Although experimental analysis is a precondition for understanding by nervous systems, it is in no way sufficient. The understanding is aided at all leve...

Small brains can completely outclass large ones in their performance. Thus the fly has proved to be an outstanding model system for image processing in the brain

A conductance-based model for synaptic transmission and postsynaptic integration reveals how postsynaptic responses and their variability depend on the number of synaptic inputs. With increasing number of balanced stochastic excitatory and inhibitory inputs, the postsynaptic responses and their variance first increase and then decrease again. This...

Synaptic transmission is usually studied in vitro with electrical stimulation replacing the natural input of the system. In contrast, we analyzed in vivo transfer of visual motion information from graded-potential presynaptic to spiking postsynaptic neurons in the fly. Motion in the null direction leads to hyperpolarization of the presynaptic neuro...

Kleine Gehirne können große Gehirne an Leistung bei weitem übertreffen. So hat sich die Fliege als hervorragendes Modellsystem für die Bildverarbeitung im Gehirn erwiesen.

Information processing in visual systems is constrained by the spatial and temporal characteristics of the sensory input and by the biophysical properties of the neuronal circuits. Hence, to understand how visual systems encode behaviourally relevant information, we need to know about both the computational capabilities of the nervous system and th...

We studied an identified motion-sensitive neuron of the blowfly under outdoor conditions. The neuron was stimulated by oscillating the fly in a rural environment. We analysed whether the motion-induced neuronal activity is affected by brightness changes ranging between bright sunlight and dusk. In addition, the relationship between spike rate and a...

Kleine Gehirne wie die von Fliegen können große Gehirne, ganz zu schweigen von technischen Systemen, in manchen Leistungen bei weitem übertreffen. Ein Beispiel ist die Schnelligkeit der visuellen Bildverarbeitung. Bei der Fliege lässt sich zur Untersuchung der visuellen Bildverarbeitung ein breites Spektrum von Forschungsansätzen anwenden, das von...

Synaptic transmission between a graded potential neuron and a spiking neuron was investigated in vivo using sensory stimulation instead of artificial excitation of the presynaptic neuron. During visual motion stimulation, individual presynaptic and postsynaptic neurons in the brain of the fly were electrophysiologically recorded together with conce...

The neural encoding of sensory stimuli is usually investigated for spike responses, although many neurons are known to convey information by graded membrane potential changes. We compare by model simulations how well different dynamical stimuli can be discriminated on the basis of spiking or graded responses. Although a continuously varying membran...

It is much debated on what time scale information is encoded by neuronal spike activity. With a phenomenological model that transforms time-dependent membrane potential fluctuations into spike trains, we investigate constraints for the timing of spikes and for synchronous activity of neurons with common input. The model of spike generation has a va...

The variability of responses of sensory neurons constrains how reliably animals can respond to stimuli in the outside world. We show for a motion-sensitive visual interneuron of the fly that the variability of spike trains depends on the properties of the motion stimulus, although differently for different stimulus parameters. (1) The spike count v...

Changes in the activity of sensory neurones carry information about a given stimulus. However, neuronal activity changes may also arise from noise sources within or outside the nervous system. Here, the reliability of encoding of visual motion information is analysed in the visual motion pathway of the fly and compared to the findings obtained in o...

Representations of optic flow are encoded in fly tangential neurons by pooling the signals of many retinotopically organized local motion-sensitive inputs as well as of other tangential cells originating in the ipsi- and contralateral half of the brain. In the so called HSE cell, a neuron involved in optomotor course control, two contralateral inpu...

The response latency of an identified motion-sensitive neuron in the blowfly visual system strongly depends on stimulus parameters. The latency decreases with increasing contrast and temporal frequency of a moving pattern, but changes only little when the pattern size and thus the number of activated inputs is increased. The latency does not only d...

Raising the head temperature within a behaviourally relevant range has strong effects on the performance of an identified neuron, the H1 neuron, in the visual motion pathway of blowflies. The effect is seen as an increase in the mean amplitude of the responses to motion under both transient and steady-state conditions, a considerable decrease in th...

Direction-selective cells in the fly visual system that have large receptive fields play a decisive role in encoding the time-dependent optic flow the animal encounters during locomotion. Recent experiments on the computations performed by these cells have highlighted the significance of dendritic integration and have addressed the role of spikes v...

In a recent study, it was concluded that natural time-varying stimuli are represented more reliably in the brain than constant stimuli are. The results presented here disagree with this conclusion, although they were obtained from the same identified neuron (H1) in the fly's visual system. For large parts of the neuron's activity range, the variabi...

Background: There is much controversy about the timescale on which neurons process and transmit information. On the one hand, a vast amount of information can be processed by the nervous system if the precise timing of individual spikes on a millisecond timescale is important. On the other hand, neuronal responses to identical stimuli often vary c...

It is often assumed that the ultimate goal of a motion-detection system is to faithfully represent the time-dependent velocity of a moving stimulus. This assumption, however, may be an arbitrary standard since the requirements for a motion-detection system depend on the task that is to be solved. In the context of optomotor course stabilization, th...

Translatory movement of an animal in its environment induces optic flow that contains information about the three-dimensional layout of the surroundings: as a rule, images of objects that are closer to the animal move faster across the retina than those of more distant objects. Such relative motion cues are used by flies to detect objects in front...

How reliably neurons convey information depends on the extent to which their activity is affected by stochastic processes which are omnipresent in the nervous system. The functional consequences of neuronal noise can only be assessed if the latter is related to the response components that are induced in a normal behavioural situation. In the prese...

Compensatory eye, head or body movements are essential to stabilize the gaze or the path of locomotion. Because such compensatory responses usually lag the sensory input by a time delay, the underlying control system is prone to instability, at least if it operates with a high gain in order to compensate disturbances efficiently. In behavioural exp...

1. Visual interneurons tuned to the motion of small objects are found in many animal species and are assumed to be the neuronal basis of figure-ground discrimination by relative motion. A well-examined example is the FD1-cell in the third visual neuropil of blowflies. This cell type responds best to motion of small objects. Motion of extended patte...

1. The FD1-cell in the visual system of the fly is an identified visual interneuron that is specifically tuned to motion of small objects. In the companion paper it was shown that this response property is mediated by one of the two CH-cells, the VCH-cell, that inhibits the FD1-cell by GABAergic synapses. Here the input organization of the two CH-c...

Many animals use relative motion to segregate objects from their background [21, 26, 28, 31, 33]. Nerve cells tuned to this visual cue have been found in various animal groups, such as insects [3, 4, 6, 24, 25], amphibians [32], birds [12, 13] and mammals [1, 14]. Well examined examples are the figure detection (FD) cells in the visual system of th...

In tethered flying houseflies (Musca domestica), the yaw torque produced by the wings is accompanied by postural changes of the abdomen and hindlegs. In free flight, these body movements would jointly lead to turning manoeuvres of the animal. By recording the yaw torque together with the lateral deflections of either the abdomen or the hindlegs, it...

It is much debated on what time scale information is encoded by neuronal spike activity. With a phenomenological model that transforms time-dependent membrane potential fluctuations into spike trains, we investigate constraints for the timing of spikes and for synchronous activity of neurons with common input. The model of spike generation has a va...

The response latency of an identified motion-sensitive neuron in the blowfly visual system strongly depends on stimulus parameters. The latency decreases with increasing contrast and temporal frequency of a moving pattern, but changes only little when the pattern size and thus the number of activated inputs is increased. The latency does not only d...

To understand the functioning of nervous systems and, in particular, how they control behaviour we must bridge many levels of complexity from molecules, cells and synapses to perception behaviour. Although experimental analysis is a precondition for understanding by nervous systems, it is in no way sufficient. The understanding is aided at all leve...