Mapping Connectivity Damage in the Case of Phineas Gage

White matter (WM) mapping of the human brain using neuroimaging techniques has gained considerable interest in the neuroscience community. Using diffusion weighted (DWI) and magnetic resonance imaging (MRI), WM fiber pathways between brain regions may be systematically assessed to make inferences concerning their role in normal brain function, influence on behavior, as well as concerning the consequences of network-level brain damage. In this paper, we investigate the detailed connectomics in a noted example of severe traumatic brain injury (TBI) which has proved important to and controversial in the history of neuroscience. We model the WM damage in the notable case of Phineas P. Gage, in whom a “tamping iron” was accidentally shot through his skull and brain, resulting in profound behavioral changes. The specific effects of this injury on Mr. Gage's WM connectivity have not previously been considered in detail. Using computed tomography (CT) image data of the Gage skull in conjunction with modern anatomical MRI and diffusion imaging data obtained in contemporary right handed male subjects (aged 25–36), we computationally simulate the passage of the iron through the skull on the basis of reported and observed skull fiducial landmarks and assess the extent of cortical gray matter (GM) and WM damage. Specifically, we find that while considerable damage was, indeed, localized to the left frontal cortex, the impact on measures of network connectedness between directly affected and other brain areas was profound, widespread, and a probable contributor to both the reported acute as well as long-term behavioral changes. Yet, while significantly affecting several likely network hubs, damage to Mr. Gage's WM network may not have been more severe than expected from that of a similarly sized “average” brain lesion. These results provide new insight into the remarkable brain injury experienced by this noteworthy patient

Absolute Values of Optical Properties (μ, μ΄, μ and DPF) of Human Head Tissue: Dependence on Head Region and Individual

BACKGROUND Absolute optical properties (i.e., the absorption coefficient, μ, and the reduced scattering coefficient, [Formula: see text]) of head tissue can be measured with frequency-domain near-infrared spectroscopy (FD-NIRS). AIM We investigated how the absolute optical properties depend on the individual subject and the head region. MATERIALS AND METHODS The data set used for the analysis comprised 31 single FD-NIRS measurements of 14 healthy subjects (9 men, 5 women, aged 33.4 ± 10.5 years). From an 8-min measurement (resting-state; FD-NIRS device: Imagent, ISS Inc.; bilateral over the prefrontal cortex, PFC, and visual cortex, VC) median values were calculated for μ and [Formula: see text] as well as the effective attenuation coefficient (μ) and the differential pathlength factor (DPF). The measurement was done for each subject one to three times with at least 24 h between the measurements. RESULTS (i) A Bayesian ANOVA analysis revealed that head region and subject were the most significant main effects on μ, [Formula: see text] and μ, as well as DPF, respectively. (ii) At the VC, μ, [Formula: see text] and μ had higher values compared to the PFC. (iii) The differences in the optical properties between PFC and VC were age-dependent. (iv) All optical properties also were age-dependent. This was strongest for the properties of the PFC compared to the VC. DISCUSSION AND CONCLUSION Our analysis demonstrates that all optical head tissue properties (μ, [Formula: see text], μ and DPF) were dependent on the head region, individual subject and age. The optical properties of the head are like a 'fingerprint' for the individual subject. Assuming constant optical properties for the whole head should be carefully reconsidered

Impact of Skull Thickness on Cerebral NIRS Oximetry in Neonates: An in silico Study

Monitoring of cerebral tissue oxygen saturation (StO2) by near-infrared spectroscopy (NIRS oximetry) has great potential to reduce the incidence of hypoxic and hyperoxic events and thus prevent long-term disabilities in preterm neonates. Since the light has to penetrate superficial layers (bone, skin and cerebrospinal fluid) before it reaches the brain, the question arises whether these layers influence cerebral StO2 measurement. We assessed this influence on the accuracy of cerebral StO2 values. For that purpose, we simulated light propagation with ‘N-layered medium’ software. It was found that with a superficial layer thickness of ≤6 mm, typical for term and preterm neonates, StO2 accurately reflects cerebral tissue oxygenation