Neurologic heuristics and artistic whimsy: the cerebral cartography of Wilder Penfield

Cortical field maps across human sensory cortex

Cortical processing pathways for sensory information in the mammalian brain tend to be organized into topographical representations that encode various fundamental sensory dimensions. Numerous laboratories have now shown how these representations are organized into numerous cortical field maps (CMFs) across visual and auditory cortex, with each CFM supporting a specialized computation or set of computations that underlie the associated perceptual behaviors. An individual CFM is defined by two orthogonal topographical gradients that reflect two essential aspects of feature space for that sense. Multiple adjacent CFMs are then organized across visual and auditory cortex into macrostructural patterns termed cloverleaf clusters. CFMs within cloverleaf clusters are thought to share properties such as receptive field distribution, cortical magnification, and processing specialization. Recent measurements point to the likely existence of CFMs in the other senses, as well, with topographical representations of at least one sensory dimension demonstrated in somatosensory, gustatory, and possibly olfactory cortical pathways. Here we discuss the evidence for CFM and cloverleaf cluster organization across human sensory cortex as well as approaches used to identify such organizational patterns. Knowledge of how these topographical representations are organized across cortex provides us with insight into how our conscious perceptions are created from our basic sensory inputs. In addition, studying how these representations change during development, trauma, and disease serves as an important tool for developing improvements in clinical therapies and rehabilitation for sensory deficits.

Functional MRI applications for intra-axial brain tumours: uses and nuances in surgical practise

PURPOSE

Functional MRI (fMRI) has well-established uses to inform risks and plan maximally safe approaches in neurosurgery. In the field of brain tumour surgery, however, fMRI is currently in a state of clinical equipoise due to debate around both its sensitivity and specificity.

MATERIALS AND METHODS

In this review, we summarise the role and our experience of fMRI in neurosurgery for gliomas and metastases. We discuss nuances in the conduct and interpretation of fMRI that, based on our practise, most directly impact fMRI's usefulness in the neurosurgical setting.

RESULTS

Illustrated examples in which fMRI in our hands directly influences the neurosurgical treatment of brain tumours include evaluating the probability and nature of functional risks, especially for language functions. These presurgical risk assessments, in turn, help to predict the resectability of tumours, select or deselect patients for awake surgery, indicate the need for neurophysiological monitoring and guide the optimal use of intra-operative stimulation mapping. A further emerging application of fMRI is in measuring functional adaptation of functional networks after (partial) surgery, of potential use in the timing of further surgery.

CONCLUSIONS

In appropriately selected patients with a clearly defined surgical question, fMRI offers a valuable complementary tool in the pre-surgical evaluation of brain tumours. However, there is a great need for standards in the administration and analysis of fMRI as much as in the techniques that it is commonly evaluated against. Surprisingly little data exists that evaluates the accuracy of fMRI not just against complementary methods, but in terms of its ultimate clinical aim of minimising post-surgical morbidity.

Muscles or Movements? Representation in the Nascent Brain Sciences

The idea that the brain is a representational organ has roots in the nineteenth century, when neurologists began drawing conclusions about what the brain represents from clinical and experimental studies. One of the earliest controversies surrounding representation in the brain was the "muscles versus movements" debate, which concerned whether the motor cortex represents complex movements or rather fractional components of movement. Prominent thinkers weighed in on each side: neurologists John Hughlings Jackson and F.M.R. Walshe in favor of complex movements, neurophysiologist Charles Sherrington and neurosurgeon Wilder Penfield in favor of movement components. This essay examines these and other brain scientists' evolving notions of representation during the first eighty years of the muscles versus movements debate (c. 1873-1954). Although participants agreed about many of the superficial features of representation, their inferences reveal deep-seated disagreements about its inferential role. Divergent epistemological commitments stoked conflicting conceptions of what representational attributions imply and what evidence supports them.

Nineteenth- and twentieth-century brain maps relating to locations and constructions of brain functions

This article is an outline of the transition in "brain maps" used to illustrate locations of cortical "centers" associated with movements, sensations, and language beginning with images from Gall and Spurzheim in the nineteenth century through those of functional magnetic resonance imaging in the twenty-first century. During the intervening years, new approaches required new brain maps to illustrate them, and brain maps helped to objectify and naturalize mental processes. One approach, electrical stimulation of the cerebral cortex-exemplified by Fritsch and Hitzig in 1870, Ferrier in 1873, and Penfield by 1937-required brain maps showing functional centers with expanded and overlapping boundaries. In another approach, brain maps that linked cortical centers to account for the complex syndromes of aphasia, apraxia, alexia, and agraphia were initially constructed by Baginsky in 1871, Wernicke in 1874, and Lichtheim in 1885, then later by Lissauer in 1890, Dejerine in 1892, and Liepmann in 1920, and eventually by Geschwind in 1965 and others through the late twentieth century. Over that intervening time, brain maps changed from illustrations of points on the cerebral cortex where movements and sensations were elicited to illustrations of areas (centers) associated with recognizable functions to illustrations of connections between those areas that account for complex symptoms occurring in clinical patients. By the end of this period, advancements in physics, mathematics, and cognitive science resulted in inventions that allowed brain maps of cortical locations derived from cognitive manipulations rather than from the usual electrical or ablative manipulations. "Mental" dependent variables became "cognitive" independent variables.

Sulcus-centered resection for focal cortical dysplasia type II: surgical techniques and outcomes

Focal cortical dysplasia type II (FCD II) is a common histopathological substrate of epilepsy surgery. Here, the authors propose a sulcus-centered resection strategy for this malformation, provide technical details, and assess the efficacy and safety of this technique. The main purpose of the sulcus-centered resection is to remove the folded gray matter surrounding a dysplastic sulcus, particularly that at the bottom of the sulcus. The authors also retrospectively reviewed the records of 88 consecutive patients with FCD II treated with resective surgery between January 2015 and December 2018. The demographics, clinical characteristics, electrophysiological recordings, neuroimaging studies, histopathological findings, surgical outcomes, and complications were collected. After the exclusion of diffusely distributed and gyrus-based lesions, 71 patients (30 females, 41 males) who had undergone sulcus-centered resection were included in this study. The mean (± standard deviation) age of the cohort was 17.78 ± 10.54 years (38 pediatric patients, 33 adults). Thirty-five lesions (49%) were demonstrated on MRI; 42 patients (59%) underwent stereo-EEG monitoring before resective surgery; and 37 (52%) and 34 (48%) lesions were histopathologically proven to be FCD IIa and IIb, respectively. At a mean follow-up of 3.34 ± 1.17 years, 64 patients (90%) remained seizure free, and 7 (10%) had permanent neurological deficits including motor weakness, sensory deficits, and visual field deficits. The study findings showed that in carefully selected FCD II cases, sulcus-centered resection is an effective and safe surgical strategy.

The anatomy of the brain - learned over the centuries

This article reports the evolution and consolidation of the knowledge of neuroanatomy through the analysis of its history. Thus, we propose to describe in a historical review to summarize the main theories and concepts that emerged throughout brain anatomy history and understand how the socio-historical context can reflect on the nature of scientific knowledge. Therefore, among the diverse scientists, anatomists, doctors, and philosophers who were part of this history, there was a strong influence of the studies of Claudius Galen (AD 129-210), Leonardo da Vinci (1452- 1519), Andreas Vesalius (1514-1564), Franciscus Sylvius (1614-1672), Luigi Rolando (1773-1831), Pierre Paul Broca (1824-1880), Carl Wernicke (1848-1905), Korbinian Brodmann (1868-1918), Wilder Penfield (1891-1976), Mahmut Gazi Yasargil (1925), and Albert Loren Rhoton Jr. (1932-2016) on the fundamentals of neuroanatomy.

Cross-cultural adaptation and psychometric properties of the Italian version of the Body Perception Questionnaire

BACKGROUND/OBJECTIVE

The purpose of this study was to cross-culturally adapt the Body Perception Questionnaire Short Form (BPQ-SF) into Italian and to assess its psychometric properties in a sample of Italian subjects.

METHODS

A forward-backward method was used for translation. 493 adults were recruited for psychometric analysis. Structural validity was assessed with confirmatory factor analysis and a hypothesis testing approach. Internal consistency was assessed by Cronbach's alpha and McDonald's omega. Measurement invariance analysis was applied with an age-matched American sample.

RESULTS

The single-factor structure fit the awareness subscale (RMSEA = .036, CFI = .983, TLI = .982). Autonomic reactivity (ANSR) was well-described by supra- and sub-diaphragmatic subscales (RMSEA = .041, CFI = .984, TLI = .982). All subscales were positively correlated (r range: .50-.56) and had good internal consistency (McDonald's Omega range: .86-.92, Cronbach's alpha range: .88-.91). Measurement invariance analysis for the Awareness model showed significant results (p<0.001) in each step (weak, strong and strict) whereas the ANSR showed significant results (p<0.001) only for the strong and strict steps.

CONCLUSIONS

Our results support the Italian version of the BPQ as having consistent psychometric properties in comparison with other languages.

Cognitive and Emotional Mapping With SEEG

Mapping of cortical functions is critical for the best clinical care of patients undergoing epilepsy and tumor surgery, but also to better understand human brain function and connectivity. The purpose of this review is to explore existing and potential means of mapping higher cortical functions, including stimulation mapping, passive mapping, and connectivity analyses. We examine the history of mapping, differences between subdural and stereoelectroencephalographic approaches, and some risks and safety aspects, before examining different types of functional mapping. Much of this review explores the prospects for new mapping approaches to better understand other components of language, memory, spatial skills, executive, and socio-emotional functions. We also touch on brain-machine interfaces, philosophical aspects of aligning tasks to brain circuits, and the study of consciousness. We end by discussing multi-modal testing and virtual reality approaches to mapping higher cortical functions.

Somatotopic Arrangement of the Human Primary Somatosensory Cortex Derived From Functional Magnetic Resonance Imaging

Functional magnetic resonance imaging (fMRI) was used to estimate neuronal activity in the primary somatosensory cortex of six participants undergoing cutaneous tactile stimulation on skin areas spread across the entire body. Differences between the accepted somatotopic maps derived from Penfield's work and those generated by this fMRI study were sought, including representational transpositions or replications across the cortex. MR-safe pneumatic devices mimicking the action of a Wartenberg wheel supplied touch stimuli in eight areas. Seven were on the left side of the body: foot, lower, and upper leg, trunk beneath ribcage, anterior forearm, middle fingertip, and neck above the collarbone. The eighth area was the glabella. Activation magnitude was estimated as the maximum cross-correlation coefficient at a certain phase shift between ideal time series and measured blood oxygen level dependent (BOLD) time courses on the cortical surface. Maximally correlated clusters associated with each cutaneous area were calculated, and cortical magnification factors were estimated. Activity correlated to lower limb stimulation was observed in the paracentral lobule and superomedial postcentral region. Correlations to upper extremity stimulation were observed in the postcentral area adjacent to the motor hand knob. Activity correlated to trunk, face and neck stimulation was localized in the superomedial one-third of the postcentral region, which differed from Penfield's cortical homunculus.

Awake brain surgery in children-review of the literature and state-of-the-art

OBJECTIVE

Awake brain surgery (ABS) is poorly reported in children as it is considered having limited indications due to age and neuropsychological aspects interfering with its feasibility and psychological outcome. The aim of this article is to review the current state-of-the-art of ABS in children and to offer an objective summary of the published literature on diversified outcome aspects of pediatric awake procedures.

METHODS

A literature review was performed using the MEDLINE (PubMed) electronic database applying the following MeSH terms to the keyword search within titles and abstracts: "awake brain surgery children," "awake brain surgery pediatric," "awake craniotomy children," "awake craniotomy pediatric," and "awake surgery children." Of the initial 753 results obtained from these keyword searches, a full text screening of 51 publications was performed, ultimately resulting in 18 eligible articles for this review.

RESULTS

A total of 18 full text articles reporting the results of 50 patients were included in the analysis. Sixteen of the 18 studies were retrospective studies, comprising 7 case series, 9 case reports, and 2 reviews. Eleven studies were conducted from anesthesiological (25 patients) and 7 from neurosurgical (25 patients) departments. Most of the patients underwent ABS for supratentorial lesions (26 patients), followed by epilepsy surgery (16 patients) and deep brain stimulation (DBS) (8 patients). The median age was 15 years (range 8-17 years). Persistent deficits occurred in 6 patients, (12%), corresponding to minor motor palsies (4%) and neuropsychological concerns (8%). An awake procedure was aborted in 2 patients (4%) due to cooperation failure and anxiety, respectively.

CONCLUSIONS

Despite well-documented beneficial aspects, ABS remains mainly limited to adults. This review confirms a reliable tolerability of ABS in selected children; however, recommendations and guidelines for its standardized implementation in this patient group are pending. Recommendations and guidelines may address diagnostic workup and intra-operative handling besides criteria of eligibility, psychological preparation, and coordinated neuropsychological testing in order to routinely offer ABS to children.

Synthesis of contraries: Hughlings Jackson on sensory-motor representation in the brain

This paper examines the concept of representation in the brain which occurs in the writings of the neurologist John Hughlings Jackson (1835-1911). Jackson was immersed in Victorian physiological psychology, a hybrid of British associationism and a reflex theory of the operation of the nervous system. Furthermore, Jackson was deeply influenced by Herbert Spencer, and I argue that Spencer's progressivist evolutionary ideas are in tension with the more mechanistic approach of the reflex theory. I also discuss Jackson's legacy in the 20th century and the longstanding debate about localisation of function in the brain.

The Montreal procedure: The legacy of the great Wilder Penfield

Wilder Penfield pioneered the early practice of brain surgery. In binding together the disciplines of neurosurgery, neurology, neuropathology, psychology, and related basic sciences, Penfield transformed our understanding of the field of neuroscience. He brought to the operating room the meticulous techniques of Sherrington, combined with methods of stimulation described by Foerster, which he complemented with expert knowledge of the neurocytology of nervous tissue. While developing surgical treatments for epilepsy, Penfield began to map the brain. He established the "Montreal procedure" for the surgical treatment of epilepsy. His scientific contributions on neurostimulation were transformative in their time and continue to resonate today. This article reviews the life of Wilder Penfield and summarizes key scientific contributions. Specifically, we detail the Montreal procedure. We additionally present a painting by Canadian artist Iris Hauser, which purports to display the hidden treasures of the human mind.

"ABC"-The Awareness-Body-Chart: A new tool assessing body awareness

Background

Despite the importance of body awareness for health and well-being there is still a lack of valid assessment tools to scan proper body awareness. To respond to the limitations of questionnaires (reading/interpretation problems) the Awareness-Body-Chart (ABC) was designed to assess body awareness by colouring 51 regions according to their awareness. The objective of this study was to investigate the psychometric characteristics of the ABC.

Methods

In a questionnaire-study, 106 students in Graz (79 females, 27 males, age median 21 (IQR 20–23) years) filled in the ABC, furthermore a German body awareness questionnaire „KEKS”, and the Beck Depression Inventory II. Factor structure, internal consistency, and retest reliability of the ABC were investigated. Correlations of the ABC with the KEKS and the Beck Depression Inventory II and comparisons of subgroups were conducted.

Results

Through factor analyses, 14 factors with clear assignments to body parts could be categorized: cranium, face, cervical/lumbar region, chest/abdomen, back, shoulder, upper arm, lower arm/elbow, hand, genital area, thigh/hip, knee, lower leg, and foot. The 14 body parts and the total score showed acceptable to high Cronbach’s alphas (α = .64 - .97). The test-retest reliability showed values between ρ = .71 and ρ = .96. The correlation of the ABC and KEKS (r = .66, p < .001) confirmed validity. Further indications of validity could be seen in comparisons of subgroups and in correlations with the Beck Depression Inventory II.

Conclusion

The ABC proved good psychometric properties with acceptable to high internal consistency, acceptable to high retest reliability and high construct validity. It is an easy-to-use tool for clinical settings and research. The ABC opens new insights into body awareness-patterns of various subgroups.

Selective Manipulation of Neural Circuits

Unraveling the complex network of neural circuits that form the nervous system demands tools that can manipulate specific circuits. The recent evolution of genetic tools to target neural circuits allows an unprecedented precision in elucidating their function. Here we describe two general approaches for achieving circuit specificity. The first uses the genetic identity of a cell, such as a transcription factor unique to a circuit, to drive expression of a molecule that can manipulate cell function. The second uses the spatial connectivity of a circuit to achieve specificity: one genetic element is introduced at the origin of a circuit and the other at its termination. When the two genetic elements combine within a neuron, they can alter its function. These two general approaches can be combined to allow manipulation of neurons with a specific genetic identity by introducing a regulatory gene into the origin or termination of the circuit. We consider the advantages and disadvantages of both these general approaches with regard to specificity and efficacy of the manipulations. We also review the genetic techniques that allow gain- and loss-of-function within specific neural circuits. These approaches introduce light-sensitive channels (optogenetic) or drug sensitive channels (chemogenetic) into neurons that form specific circuits. We compare these tools with others developed for circuit-specific manipulation and describe the advantages of each. Finally, we discuss how these tools might be applied for identification of the neural circuits that mediate behavior and for repair of neural connections.

Optimizing glioblastoma resection: intraoperative mapping and beyond

The management of glioblastomas starts with surgical resection if possible, along with subsequent chemotherapy and radiation therapy. Several retrospective studies have suggested that extent of resection plays a role in the prognosis of glioblastoma patients. The importance of extent of resection must be balanced with preserving patient's functional status for tumors in eloquent areas. Here we review the preoperative imaging modalities such as functional MRI and magnetoencephalography (MEG), and the intraoperative techniques such as motor and language mapping, intraoperative MRI, and intraoperative techniques such as 5-aminolevulinic acid administration, that allow maximal safe operative resection of glioblastomas.

Letter to the Editor: reexamining Penfield's Homunculus

Snyder and Whitaker's (2013) discussion of Penfield's homunculus in a recent issue of this journal was stimulating but I believe mistaken in several ways. This letter clarifies the diagram's supposed ambiguity, highlights a largely overlooked problem with improper scaling and challenges the authors' argument for the superiority of the 1950 version of the image.