Using Extinction-Renewal to Circumvent the Memory Strength Boundary Condition in Fear Memory Reconsolidation

Reconsolidation is a process by which memories are destabilized, updated, and then restabilized. Strong memories are resistant to undergoing reconsolidation. Here, we addressed whether an overtrained fear memory could be made susceptible to reconsolidation by first extinguishing, and then renewing, the memory. Rats were trained with ten tone-footshock pairings, followed by eight days of tone extinction in the training context. The next day, rats were placed into a second context and memory for the tone was renewed/reactivated with a single tone presentation. Immediately following reactivation, rats received an injection of midazolam or vehicle. Rats were then tested for freezing to the tone in a third context. Midazolam had no effect in rats that did not undergo tone extinction, but significantly attenuated freezing to the tone in extinguished rats. Thus, rats that received tone extinction underwent tone memory reconsolidation following its renewal. In a second experiment, we administered the reactivation session and midazolam injections prior to extinction. Midazolam had no effect and rats extinguished at a rate similar to controls. These data suggest that strong emotional memories are capable of updating following weakening of memory expression through extinction.

High-Accuracy Parameter Estimation for Damped Signal via Three Weighted DFT Samples

Recently, accurate parameter estimation of the damped complex exponential plays an increasingly important role in the field of precise measurement. However, the estimation variance of interpolation-based algorithms for the parameter estimation cannot be asymptotic to the Crámer-Rao lower bound (CRLB). This paper originally proposes a generalized, fast, and the accurate two-iteration estimator (TIE) based on the discrete Fourier transform (DFT). It can be operated by an arbitrary window (symmetric or asymmetric window). Theoretical estimation variances of the frequency and the damping factor for arbitrary windows are derived, respectively. Furthermore, extensive computer simulations are performed to compare the performance of the TIE with other state-of-the-art algorithms in the literature. The results support the theoretical findings and verify that high-accuracy parameter estimation can be ensured by the proposed algorithm. More importantly, the estimation variances returned by the TIE with the rectangle window exactly track the CRLB for a damped single tone.

Learning the Special Note: Evidence for a critical period for absolute pitch acquisition

Children (3–6 years old) and adults were trained for 6 weeks to identify a single tone, C5. Test sessions, held at the end of each week, had participants identify C5 within a set of seven alternative tones. By the third week of training, identification accuracy of children 5–6 years old surpassed the accuracies of children 3–4 years old and adults. Combined with an analysis of perceptual strategies, the data provide strong support for a critical period for absolute pitch acquisition.

Learning the Special Note: Evidence for a critical period for absolute pitch acquisition

Children (3–6 years old) and adults were trained for 6 weeks to identify a single tone, C5. Test sessions, held at the end of each week, had participants identify C5 within a set of seven alternative tones. By the third week of training, identification accuracy of children 5–6 years old surpassed the accuracies of children 3–4 years old and adults. Combined with an analysis of perceptual strategies, the data provide strong support for a critical period for absolute pitch acquisition.

Comparisons in Frequency Difference Limens Between Sequential and Simultaneous Listening Conditions in Normal-Hearing Listeners

Purpose We compared frequency difference limens (FDLs) in normal-hearing listeners under two listening conditions: sequential and simultaneous. Method Eighteen adult listeners participated in three experiments. FDL was measured using a method of limits for comparison frequency. In the sequential listening condition, the tones were presented with a half-second time interval in between, but for the simultaneous listening condition, the tones were presented simultaneously. For the first experiment, one of four reference tones (125, 250, 500, or 750 Hz), which was presented to the left ear, was paired with one of four starting comparison tones (250, 500, 750, or 1000 Hz), which was presented to the right ear. The second and third experiments had the same testing conditions as the first experiment except with two- and three-tone complexes, comparison tones. The subjects were asked if the tones sounded the same or different. When a subject chose “different,” the comparison frequency decreased by 10% of the frequency difference between the reference and comparison tones. FDLs were determined when the subjects chose “same” 3 times in a row. Results FDLs were significantly broader (worse) with simultaneous listening than with sequential listening for the two- and three-tone complex conditions but not for the single-tone condition. The FDLs were narrowest (best) with the three-tone complex under both listening conditions. FDLs broadened as the testing frequencies increased for the single tone and the two-tone complex. The FDLs were not broadened at frequencies > 250 Hz for the three-tone complex. Conclusion The results suggest that sequential and simultaneous frequency discriminations are mediated by different processes at different stages in the auditory pathway for complex tones, but not for pure tones.

Axial stiffness identification of a ball screw feed system using generalized frequency response functions

Contact of balls in screw nuts and bearings causes the nonlinearity of a ball screw feed system. The identification of nonlinear stiffness helps to understand and control the feed system. The axial vibration of the ball screw feed system can be descripted by a single-degree-of-freedom (SDOF) system with polynomial nonlinear terms. Since generalized frequency response functions (GFRFs) can be expressed in terms of linear and nonlinear system parameters, one can estimate these parameters based on the measured GFRFs. In this effort, both single-tone and multitone harmonic inputs are employed to measure GFRFs, and a simple search algorithm is proposed to find the suitable frequency set of the multitone input. Parameter identification based on these two methods has been compared by numerical simulation and experiment. Since the response spectrum measured from vibration experiment of a ball screw system has even and odd harmonics, it is suitable to simplify the restoring force with square and cubic nonlinearity form. Static experiment is also conducted to verify the identified parameters, and the results show that the method based on single-tone inputs performs effectively in identifying axial stiffness of a ball screw feed system, but the method based on multitone inputs gets the incorrect results in practical application