The ability to determine the location of a sound source is fundamental to hearing. However, auditory space is not represented in any systematic manner on the basilar membrane of the cochlea, the sensory surface of the receptor organ for hearing. Understanding the means by which sensitivity to spatial cues is computed in central neurons can therefore contribute to our understanding of the basic nature of complex neural representations. We review recent evidence concerning the nature of the neural representation of auditory space in the mammalian brain and elaborate on recent advances in the understanding of mammalian subcortical processing of auditory spatial cues that challenge the "textbook" version of sound localization, in particular brain mechanisms contributing to binaural hearing.

Mechanisms of Sound Localization in Mammals

Summary: Purpose: Depth electrodes recordings may be required in some cases of epilepsy surgery to delineate the best region for cortical resection. We usually implant depth electrodes according to Talairach’s stereoelectroencephalography (SEEG) method. By using these permanently implanted depth electrodes, we are able to perform radiofrequency (RF)-thermolesions of the epileptic foci. We report the technical data required to perform such multiple cortical thermolesions, as well as preliminary results in terms of seizure outcome in a group of 20 patients. Methods: Lesions were performed by using 100- to 110-mA bipolar current (50 V), applied for 10 to 50 s. Each thermocoagulation produced a 5- to 7-mm diameter cortical lesion. In total, two to 16 lesions were performed in each of the 20 patients. Lesions were placed without anesthesia. No general or neurologic complication occurred during the procedures. Two transient postprocedure side effects, consisting of paresthetic sensations in the mouth and mild apraxia of the hand, were observed. Results: At a follow-up time of 8 to 31 months (mean, 19 months), 15% of the patients became seizure free, 40% experienced a ≥80% reduction of their seizure frequency, and 45% were not significantly improved. Conclusions: SEEG-guided RF thermolesions is a safe technique. Our preliminary results indicate that such lesions can lead to a significant reduction of seizure frequency and could be proposed as a palliative procedure if no resective surgery is possible. A randomized controlled trial is needed to determine which patients are likely to respond to SEEG-guided RF ther

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.0013-9580.2004.17704.x

SEEG-guided RF thermocoagulation of epileptic foci: feasibility, safety, and preliminary results.

Summary: Purpose: This study was carried out to assess the safety and efficacy of stereotactic ablation of the amygdala and hippocampus for the treatment of medial temporal lobe epilepsy.



Methods: Twenty-two stereotactic amygdalohippocampotomies were performed in 19 patients with unilateral temporal lobe seizures by using magnetic resonance imaging (MRI) localization for target planning and radiofrequency techniques for lesion production. Seizure frequency was assessed at 3-monthly follow-up visits. Two lesion groups were defined. In group I, four to 11 (mean, 6.4) discrete lesions were made, encompassing the amygdala and anterior 13–21 mm (mean, 16.8 mm) of the hippocampus. In group II, a large number of confluent lesions were made (mean, 26.0; range, 12–54) encompassing the amygdala and anterior 15–34 mm (mean, 21.5 mm) of the hippocampus. MRI scanning was carried out 24 h and 6–9 months after surgery.



Results: In five group I patients, one (20%) experienced a favorable seizure outcome. Of 15 group II patients, one of whom had previously undergone limited lesioning and was also analyzed as part of group I, nine (60%) experienced a favorable seizure outcome, with two seizure free. MRI scans at 6- to 9-months’follow-up disclosed discrete areas of atrophy in the amygdala and hippocampus, interspersed with preserved brain in the group I patients. More uniform and complete destruction of amygdala and hippocampus was evident in group II patients. All lesions were confined to the amygdala and hippocampus, sparing the parahippocampal gyrus (PHG).



Conclusions: The extensive amygdalohippocampal ablation in group II patients improved seizure outcome compared with more limited ablation in group I, but these results were not so good as those from temporal lobectomy in a similar patient group. When considered together with the results of selective amygdalohippocampectomy, and temporal resections that spare hippocampus or amygdala (all producing similar outcomes, and all involving resection of the entorhinal cortex), this study suggests a pivotal role of the entorhinal cortex in temporal epileptogenesis.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1528-1157.1999.tb02013.x

Stereotactic amygdalohippocampotomy for the treatment of medial temporal lobe epilepsy

1.

Phonotactic approaches (N=156) of 42 female green treefrogs (Hyla cinerea) were videotaped over a distance of 3.75 m in response to synthetic mating calls (0.9 kHz and 0.9, 2.7 and 3.0 kHz).




2.

To quantify the accuracy of phonotaxis, jump anglesγ and head orientation angles α were measured (Fig. 2) when the animals were 1 m or farther from the sound source.




3.

Phonotaxis was extremely accurate in response to the 3-component call, which is behaviorally equivalent to the male's natural mating call. The mean jump angle was\(\bar \gamma = 16.1^\circ\) (Fig. 5). Head scanning occurred prior to about 25% of the jumps. The accuracy of head orientation after scanning was even greater\((\bar \alpha = 8.4^\circ )\) as were the subsequent jumps\((\bar \gamma = 11.8^\circ )\) (Fig. 6 and Table 1).




4.

With respect to the two synthetic calls no statistically significant differences in jump accuracy were found (Table 1). Thus the high frequency components around 3 kHz, normally found in the mating call, do not enhance the accuracy of sound localization.




5.

Our results are discussed in terms of models of sound localization in vertebrates and invertebrates, and we suggest that the treefrog's ear must act as a sound pressure gradient receiver.

Accuracy of phonotaxis by the green treefrog (Hyla cinerea)

We review the human literature examining the effects of neurological insult on human sexual behaviour. We provide a synthesis of the findings to date, and identify key brain regions associated with specific aspects of human sexual behaviour. These include subcortical and cortical regions, with the mesial temporal lobe and the amygdala in particular being a crucial structure in the mediation of human sexual drive.

https://jnnp.bmj.com/content/jnnp/78/10/1042.full.pdf

Neurological control of human sexual behaviour: insights from lesion studies

58 patients, whose convulsions and behavioral disorders did not respond to nonsurgical therapy, were treated with stereotactic amygdalotomy between 1963 and 1973. A retrospective study was carried out

R.F. Heimburger

Papers

Stereotactic Amygdalotomy for Convulsive and Behavioral Disorders

Follow-up of stereotaxic amygdalotomy for seizure and behavior disorders.