Lennart Heimer died on March 5, 2007, at the age of 77, in Charlottesville, Virginia. With his death, we lost one of the last towering figures of 20th century neuroanatomy. He contributed in many ways to the advances of neuroscience, including the development of one of the most successful neuronal tracing methods (Fink and Heimer 1967). In addition to introducing new concepts to understand the synaptic connections of a large enigmatic basal forebrain area, the substantia innominata, he also contributed to the deciphering of the connections of many brain regions, including the amygdala, olfactory bulb, thalamus, hypothalamus and the cerebral cortex. He was an enthusiastic teacher of generations of medical students, psychiatry and neurosurgery residents; his unique ability to seamlessly connect brain macroanatomy to synaptic connections and functions was a gift shared only by the giants of this last century. The first edition of his textbook in 1981 was really a succession of his much earlier text book that was published in Swedish in 1961. Unfortunately, the second edition of his textbook and its accompanying videotapes (1995) are no longer available, but with unwavering efforts he was still busy editing two new DVDs about his favorite topic, the dissection of the human brain, even in the hospital bed.
Bob Switzer, one of Lennart’s coworkers in the late 1970s founded one of the most successful biotech company (NeuroScience Associates) in part in response to this need.
He was especially fond of the various combined techniques that facilitate direct rather than indirect identification of a nerve element or chains of connections in their natural environment (Hardy et al. 1976; de Olmos and Heimer 1980; Alheid et al. 1984a, b; Zaborszky et al. 1985b; Zaborszky and Heimer 1989; Schmued et al. 1990). The chapters, including his own with his coworkers, in the two editions of ‘Neuroanatomical Tract-tracing’ (Heimer and Robards 1981; Heimer and Zaborszky 1989) had a tremendous impact on neuroscience and are still among the most frequently consulted laboratory textbooks. Although he was not able to participate in the preparation of the third edition (Zaborszky, Wouterlood, Lanciego, editors, Springer 2006), he was keenly interested and summarized his thoughts in a ‘Short Retrospection’ as an introduction to the original contributions of this volume (Heimer 2006).
The olfactory tubercle is located on the base of the brain and using dorsal approach, the accidental damage to structures that are penetrated by the electrode would complicate the interpretation of the results due to the ‘fibers of passage’ problem caused by lesions, therefore Lennart used a heat lesion apparatus (Heimer and Lohman 1976) to produce superficial lesion and a ventral approach aided by his stereotaxic apparatus, he developed with Knut Larsson (Heimer et al. 1971).
See in more detail the Introduction and the relevant chapters in the Advancing from the Ventral Striatum to the Extended Amygdala. Implications for neuropsychiatry and drug abuse. A NYAS conference in honor of Lennart Heimer. vol 877, Ann N Y Acad Sci 1999 (edited by McGinty). Also, see the paper of Walker and Davis and Smith and Aston-Jones in this volume.
Using the cupric-silver technique of de Olmos (1969), the gray matter located in the subpallidal (sublenticular) substantia innominata shows similar staining pattern as the bed nucleus of the stria terminalis and the centromedial amygdala (de Olmos 1972). Jose de Olmos passed away in January 2008, just a few days after he submitted his paper for this special issue as a tribute to his friend, Lennart Heimer.
He argued that the term substantia innominata was too vague and should be abandoned since parts of it belongs to better characterized nearby systems, such as the ventral striato-pallidal system, the nucleus basalis and the extended amygdala.
