Here, we systematically explore the size and spacing requirements for identifying a letter among other letters. We measure acuity for flanked and unflanked letters, centrally and peripherally, in normals and amblyopes. We find that acuity, overlap masking, and crowding each demand a minimum size or spacing for readable text. Just measuring flanked and unflanked acuity is enough for our proposed model to predict the observer's threshold size and spacing for letters at any eccentricity. We also find that amblyopia in adults retains the character of the childhood condition that caused it. Amblyopia is a developmental neural deficit that can occur as a result of either strabismus or anisometropia in childhood. Peripheral viewing during childhood due to strabismus results in amblyopia that is crowding limited, like peripheral vision. Optical blur of one eye during childhood due to anisometropia without strabismus results in amblyopia that is acuity limited, like blurred vision. Furthermore, we find that the spacing:acuity ratio of flanked and unflanked acuity can distinguish strabismic amblyopia from purely anisometropic amblyopia in nearly perfect agreement with lack of stereopsis. A scatter diagram of threshold spacing versus acuity, one point per patient, for several diagnostic groups, reveals the diagnostic power of flanked acuity testing. These results and two demonstrations indicate that the sensitivity of visual screening tests can be improved by using flankers that are more tightly spaced and letter like. Finally, in concert with Strappini, Pelli, Di Pace, and Martelli (submitted), we jointly report a double dissociation between acuity and crowding. Two clinical conditions-anisometropic amblyopia and apperceptive agnosia-each selectively impair either acuity A or the spacing:acuity ratio S/A, not both. Furthermore, when we specifically estimate crowding, we find a double dissociation between acuity and crowding. Models of human object recognition will need to accommodate this newly discovered independence of acuity and crowding.
Interactions between direction-selective mechanisms for motion were examined in strabismic and anisometropic amblyopia. Amblyopes were found to have a marked reduction in sensitivity to flicker or movement when the amblyopic eye was presented with a combination of two gratings drifting in opposite directions at the same velocity (i.e., a counterphase grating). Sensitivity to flicker of the counterphase grating was improved by preadapting the amblyopic eyes to a single grating which was drifting nasalward, but there was no improvement if the drift of the adapting grating was temporalward. Sensitivity to flicker was also improved by reducing field size from 10 degrees to 3 degrees. However, occluding the central 4 degrees of the 10 degrees field did not significantly alter the sensitivity to flicker. These data suggest that inhibition between motion detectors in the parafovea of amblyopic eyes reduces slow-motion perception in both the parafovea and the fovea. The results also demonstrated a reduction in amblyopic eyes of direction slectivity for motion detection.
This paper focuses on room fingerprinting, a task involving the analysis of an audio recording to determine the specific volume and shape of the room in which it was captured. While it is relatively straightforward to determine the basic room parameters from the Room Impulse Responses (RIR), doing so from a speech signal is a cumbersome task. To address this challenge, we introduce a dual-encoder architecture that facilitates the estimation of room parameters directly from speech utterances. During pre-training, one encoder receives the RIR while the other processes the reverberant speech signal. A contrastive loss function is employed to embed the speech and the acoustic response jointly. In the fine-tuning stage, the specific classification task is trained. In the test phase, only the reverberant utterance is available, and its embedding is used for the task of room shape classification. The proposed scheme is extensively evaluated using simulated acoustic environments.
Practice improves contrast discrimination by a factor of two if Gabor stimuli of various contrasts are presented in blocked trials (Yu, Klein & Levi, VSS03, JOV04). However, no significant learning is evident when stimuli are temporally randomly interleaved (Sagi et al, VSS03; Yu et al, VSS03, JOV04). Recently we studied the factors limiting the effective learning of contrast discrimination and found that, among many stimulus properties (stimulus duration, simultaneous vs. successive presentation, same vs. different retinal locations for different contrasts, etc.), the temporal pattern of stimulus contrasts is the key for contrast discrimination learning. When stimulus contrasts are interleaved temporally in an ascending ramp pattern, contrast discrimination can be improved by practice nearly as much as in the blocked trials condition. To determine whether contrast discrimination learning is due to the temporal stimulus pattern itself or due to the fact that the subject are aware of the stimulus contrast before each interleaved trial, we had subjects practice the random interleaving condition with additional exogenous cueing (an identical Gabor at the same contrast) or endogenous cueing (letters ABCD representing four contrasts levels) preceding each trial. No significant improvement of contrast discrimination is shown in either cueing condition. Evidently cueing does not produce memory trace useful for establishing a contrast template. Our surprising results eliminate the role of contrast uncertainty in contrast learning and point to a role of temporal patterning — but stay tuned.
Adult amblyopes can improve positional acuity through practice; however, the neural mechanisms underlying this improvement are still not clear. In this study, seven adult amblyopes repeatedly practiced a position discrimination task in the presence of positional noise. We found that six of the seven showed systematic and significant improvements in position acuity that were both eye and orientation specific. Using a position-averaging model, we were able to parse the improvement in performance with practice into two factors: improvement in sampling efficiency and reduction of equivalent input noise. Three of the seven showed improved efficiency with no change in equivalent noise, two showed a significant reduction in equivalent noise with no change in efficiency, and one showed both improved efficiency and reduced equivalent noise. Interestingly, all observers showed substantial improvement in visual acuity, and one observer showed substantial improvement in stereoacuity. Three observers were also tested on a counting task, and all three improved after practicing positional discrimination. Our results reveal the mechanisms underlying perceptual learning in amblyopic vision, and may provide a basis for developing more effective and efficient strategies for the treatment of amblyopia.
Accurate and reliable identification of the RTF between microphones with respect to a desired source is an essential component in the design of microphone array beamformers, specifically the MVDR criterion. Since an accurate estimation of the RTF in a noisy and reverberant environment is a cumbersome task, we aim at leveraging prior knowledge of the acoustic enclosure to robustify the RTF estimation by learning the RTF manifold. In this paper, we present a novel robust RTF identification method, tested and trained with real recordings, which relies on learning the RTF manifold using a GCN to infer a robust representation of the RTF in a confined area, and consequently enhance the beamformer's performance.
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